diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 4a8ccfca3..b5d04bbe2 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -65,6 +65,18 @@ jobs:
     - name: Checkout repository
       uses: actions/checkout@v3
 
+    - name: Clone flatpak manifest from Flathub
+      uses: GuillaumeFalourd/clone-github-repo-action@v2
+      with:
+        owner: 'flathub'
+        repository: 'com.github.Murmele.Gittyup'
+
+    # just until the new release is out
+    - name: Checkout restructureCMake
+      run: |
+        cd com.github.Murmele.Gittyup
+        git checkout Qt6
+
     - name: Replace git tag by the commit id on which it runs
       if: github.ref_type != 'tag'
       run: >
@@ -120,11 +132,7 @@ jobs:
       fail-fast: false
       matrix:
         qt:
-          - version: 5.15.2
-            check_only: false
-
-          - version: 5.12.0
-            check_only: true
+          - version: 6.5.3
 
         env:
           - name: linux
@@ -161,23 +169,6 @@ jobs:
               CXX: clang++
             pack: 1
 
-          - name: win32
-            os: windows-latest
-            ninja_platform: win
-            qt_platform: windows
-            qt_arch: win32_msvc2019
-            qt_arch_check_only: win32_msvc2017
-            openssl_arch: VC-WIN32
-            msvc_arch: x86
-            cmake_flags: "-DUSE_BUNDLED_ZLIB=1"
-            cmake_env:
-              CMAKE_RC_FLAGS: "/C 1252"
-              CC: clang
-              CXX: clang++
-              CMAKE_C_FLAGS: -m32
-              CMAKE_CXX_FLAGS: -m32
-            pack: 1
-
     steps:
       # otherwise the testcases will fail, because signature is invalid
       - name: Set git name and email
@@ -206,7 +197,6 @@ jobs:
       - name: Install Qt
         uses: jurplel/install-qt-action@v3.3.0
         timeout-minutes: 10
-        if: "!matrix.qt.check_only"
         with:
           version: ${{ matrix.qt.version }}
           target: desktop
@@ -215,18 +205,6 @@ jobs:
           install-deps: true
           modules: qtwebengine
 
-      - name: Install Qt
-        uses: jurplel/install-qt-action@v3.3.0
-        timeout-minutes: 10
-        if: matrix.qt.check_only
-        with:
-          version: ${{ matrix.qt.version }}
-          target: desktop
-          host: ${{ matrix.env.qt_platform }}
-          arch: ${{ matrix.env.qt_arch_check_only }}
-          install-deps: true
-          modules: qtwebengine
-
       - name: Install Ninja
         uses: seanmiddleditch/gha-setup-ninja@v4
         with:
@@ -256,10 +234,6 @@ jobs:
         run: |
           cd dep/openssl/openssl
 
-          # this is necessary until https://github.com/openssl/openssl/issues/18720
-          # is fixed in OpenSSL 1.1.1r
-          export CFLAGS=-Wno-error=implicit-function-declaration
-
           ./Configure ${{ matrix.env.openssl_arch }} no-shared
           make
 
@@ -291,7 +265,7 @@ jobs:
 
       # Command copied from flathub build process
       - name: Validate appdata file
-        if: matrix.env.ninja_platform == 'linux' && !matrix.qt.check_only
+        if: matrix.env.ninja_platform == 'linux'
         run: |
           echo "Show generated appdata file"
           cat ./build/release/rsrc/linux/com.github.Murmele.Gittyup.appdata.xml
@@ -302,14 +276,14 @@ jobs:
           flatpak run --env=G_DEBUG=fatal-criticals org.freedesktop.appstream-glib validate ./build/release/rsrc/linux/com.github.Murmele.Gittyup.appdata.xml
 
       - name: Publish build artifacts
-        if: matrix.env.pack && !matrix.qt.check_only
+        if: matrix.env.pack
         uses: actions/upload-artifact@v3
         with:
           path: build/release/pack/Gittyup-*
           name: Gittyup ${{ matrix.env.name }}
 
       - name: Publish version file
-        if: matrix.env.pack && !matrix.qt.check_only
+        if: matrix.env.pack
         uses: actions/upload-artifact@v3
         with:
           path: build/release/Version.txt
@@ -334,12 +308,12 @@ jobs:
           ninja check_no_win32_offscreen
 
       - name: Build Appimage
-        if: matrix.env.ninja_platform == 'linux' && !matrix.qt.check_only
+        if: matrix.env.ninja_platform == 'linux'
         run: |
           cd build/release
           sudo apt -y install appstream
           sudo apt -y install libfuse2
-          sudo apt -y install libxcb-icccm4 libxcb-image0 libxcb-keysyms1 libxcb-randr0 libxcb-render-util0 libxcb-shape0
+          sudo apt -y install libxcb-icccm4 libxcb-image0 libxcb-keysyms1 libxcb-randr0 libxcb-render-util0 libxcb-shape0 libxcb-cursor0 libxkbcommon0 libx11-xcb1
           sudo apt -y install libxcb-shm0 libxcb-sync1 libxcb-util1 libxcb-xinerama0 libxcb-xinput0 libxcb-xkb1 libxcb-xrm0 libxcb-xv0 libxcb-xvmc0 libxcb1
           
           mkdir -p AppDir
@@ -352,6 +326,12 @@ jobs:
 
           wget -c https://github.com/$(wget -q https://github.com/probonopd/go-appimage/releases/expanded_assets/continuous -O - | grep "appimagetool-.*-x86_64.AppImage" | head -n 1 | cut -d '"' -f 2)
           chmod +x appimagetool-*.AppImage
+          echo Show QTDIR
+          ls $QTDIR
+          echo Show QTDIR plugins
+          ls $QTDIR/plugins
+          echo Show QTDIR plugins platforms
+          ls $QTDIR/plugins/platforms
           QTDIR=$QTDIR ./appimagetool-*.AppImage -s deploy ./AppDir/usr/share/applications/*.desktop --appimage-extract-and-run # Bundle EVERYTHING
 
           # Modify the AppDir: move ld-linux into the same directory as the payload application
@@ -365,7 +345,7 @@ jobs:
           #ls -lh Gittyup-*
 
       - name: Publish Appimage
-        if: matrix.env.ninja_platform == 'linux' && !matrix.qt.check_only
+        if: matrix.env.ninja_platform == 'linux'
         uses: actions/upload-artifact@v3
         with:
           path: build/release/*.AppImage
@@ -402,7 +382,6 @@ jobs:
           automatic_release_tag: 'development'
           files: |
             **/artifacts/Gittyup win64/Gittyup*.exe
-            **/artifacts/Gittyup win32/Gittyup*.exe
             **/artifacts/Gittyup macos/Gittyup*.dmg
             **/artifacts/GittyupFlatpak/*.flatpak
             **/artifacts/GittyupAppImage/Gittyup*.AppImage
@@ -417,7 +396,6 @@ jobs:
           automatic_release_tag: ${{ github.ref_name }}
           files: |
             **/artifacts/Gittyup win64/Gittyup*.exe
-            **/artifacts/Gittyup win32/Gittyup*.exe
             **/artifacts/Gittyup macos/Gittyup*.dmg
             **/artifacts/GittyupFlatpak/*.flatpak
             **/artifacts/GittyupAppImage/Gittyup*.AppImage
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4bd47318e..a1ce27660 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -114,14 +114,10 @@ else()
 endif()
 
 find_package(
-  Qt5 5.12
+  Qt6
   COMPONENTS ${QT_MODULES} LinguistTools
   REQUIRED)
 if(FLATPAK)
-  find_package(
-    Qt5 5.15
-    COMPONENTS XcbQpa
-    REQUIRED)
   add_compile_definitions(FLATPAK)
 endif()
 
@@ -135,7 +131,7 @@ endif()
 
 include(GNUInstallDirs) # Defines some variables as BINDIR, LIBDIR, ...
 
-set(QT_TRANSLATIONS_DIR "${Qt5_DIR}/../../../translations")
+set(QT_TRANSLATIONS_DIR "${Qt6_DIR}/../../../translations")
 set(QT_TRANSLATIONS_DIR "/usr/share/qt/translations")
 
 if(APPLE)
@@ -145,8 +141,8 @@ if(APPLE)
     # dependencies are to the release libraries (e.g. QtGui_debug depends on
     # QtCore). This causes multiple symbol definition errors at application load
     # time.
-    get_target_property(LOCATION Qt5::${QT_MODULE} LOCATION)
-    set_target_properties(Qt5::${QT_MODULE} PROPERTIES IMPORTED_LOCATION_DEBUG
+    get_target_property(LOCATION Qt6::${QT_MODULE} LOCATION)
+    set_target_properties(Qt6::${QT_MODULE} PROPERTIES IMPORTED_LOCATION_DEBUG
                                                        ${LOCATION})
   endforeach()
 endif()
diff --git a/com.github.Murmele.Gittyup.yml b/com.github.Murmele.Gittyup.yml
index 32f8b0f11..dfa892ec9 100644
--- a/com.github.Murmele.Gittyup.yml
+++ b/com.github.Murmele.Gittyup.yml
@@ -1,6 +1,6 @@
 app-id: com.github.Murmele.Gittyup
 runtime: org.kde.Platform
-runtime-version: 5.15-23.08
+runtime-version: 6.7
 sdk: org.kde.Sdk
 command: gittyup
 desktop-file-name-suffix: "" # used to create development version
diff --git a/dep/openssl/openssl b/dep/openssl/openssl
index 3f499b24f..1c01dbcbe 160000
--- a/dep/openssl/openssl
+++ b/dep/openssl/openssl
@@ -1 +1 @@
-Subproject commit 3f499b24f3bcd66db022074f7e8b4f6ee266a3ae
+Subproject commit 1c01dbcbebc08d629d02326d941b8491ae99597d
diff --git a/dep/scintilla/CMakeLists.txt b/dep/scintilla/CMakeLists.txt
index a7a11972c..9de63ddd1 100644
--- a/dep/scintilla/CMakeLists.txt
+++ b/dep/scintilla/CMakeLists.txt
@@ -54,7 +54,7 @@ target_compile_definitions(
 
 target_include_directories(scintilla PUBLIC ${SCINTILLA_DIR}/src)
 
-target_link_libraries(scintilla Qt5::Widgets lexilla)
+target_link_libraries(scintilla Qt6::Widgets lexilla)
 
 set_target_properties(scintilla PROPERTIES AUTOMOC ON)
 
diff --git a/l10n/CMakeLists.txt b/l10n/CMakeLists.txt
index 14543f0bb..dfd68fc63 100644
--- a/l10n/CMakeLists.txt
+++ b/l10n/CMakeLists.txt
@@ -28,9 +28,9 @@ configure_file("${CMAKE_CURRENT_SOURCE_DIR}/languages.cpp.inc"
 
 if(UPDATE_TRANSLATIONS)
   # FIXME: Clean removes the .ts files.
-  qt5_create_translation(QM_FILES ${SOURCE_FILES} ${TS_FILES})
+  qt6_create_translation(QM_FILES ${SOURCE_FILES} ${TS_FILES})
 else()
-  qt5_add_translation(QM_FILES ${TS_FILES})
+  qt6_add_translation(QM_FILES ${TS_FILES})
 endif()
 
 add_custom_target(translations DEPENDS ${QM_FILES})
@@ -38,7 +38,7 @@ add_dependencies(gittyup translations)
 
 add_library(translation ${LANGUAGE_SOURCE_FILE})
 target_include_directories(translation PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}")
-target_link_libraries(translation Qt5::Core)
+target_link_libraries(translation Qt6::Core)
 
 # install language files
 
diff --git a/pack/CMakeLists.txt b/pack/CMakeLists.txt
index c9b5f4de4..fac5dac7f 100644
--- a/pack/CMakeLists.txt
+++ b/pack/CMakeLists.txt
@@ -28,13 +28,13 @@ if(FLATPAK)
   qt_import_plugins(gittyup INCLUDE ${QT_PLUGINS})
 elseif(NOT USE_SYSTEM_QT)
   foreach(QT_PLUGIN ${QT_PLUGINS})
-    if(NOT TARGET Qt5::${QT_PLUGIN})
+    if(NOT TARGET Qt6::${QT_PLUGIN})
       if(UNIX OR APPLE)
         continue()
       endif()
     endif()
 
-    get_target_property(PLUGIN Qt5::${QT_PLUGIN} LOCATION_${CMAKE_BUILD_TYPE})
+    get_target_property(PLUGIN Qt6::${QT_PLUGIN} LOCATION_${CMAKE_BUILD_TYPE})
     get_filename_component(FILE_NAME ${PLUGIN} NAME)
     get_filename_component(DIR ${PLUGIN} DIRECTORY)
     get_filename_component(DIR_NAME ${DIR} NAME)
@@ -78,11 +78,16 @@ elseif(NOT USE_SYSTEM_QT)
 
   # Install Qt libraries.
   foreach(QT_MODULE ${QT_MODULES})
-    get_target_property(QT_LIBRARY Qt5::${QT_MODULE}
+    get_target_property(QT_LIBRARY Qt6::${QT_MODULE}
                         LOCATION_${CMAKE_BUILD_TYPE})
 
     if(APPLE)
       get_filename_component(QT_FRAMEWORK ${QT_LIBRARY} DIRECTORY)
+
+      # FIXME: QT_LIBRARY points directly to the library bin instead of the
+      # symlink 2 directories above (since qt6)
+      string(REGEX REPLACE "/Versions/.*" "" QT_FRAMEWORK "${QT_FRAMEWORK}")
+
       set(DEST_DIR ${CONTENTS_DIR}/Frameworks)
       install(
         DIRECTORY ${QT_FRAMEWORK}
@@ -102,7 +107,7 @@ elseif(NOT USE_SYSTEM_QT)
       else()
         # Strip minor and patch version extensions.
         get_filename_component(TARGET_NAME_WE ${QT_LIBRARY} NAME_WE)
-        set(TARGET_NAME ${TARGET_NAME_WE}.so.5)
+        set(TARGET_NAME ${TARGET_NAME_WE}.so.6)
       endif()
 
       install(
@@ -131,8 +136,8 @@ endif()
 
 # Install XcbQpa library.
 if(UNIX AND NOT APPLE)
-  set(LIB_NAME libQt5XcbQpa)
-  get_target_property(QT_CORE_LIBRARY Qt5::Core LOCATION)
+  set(LIB_NAME libQt6XcbQpa)
+  get_target_property(QT_CORE_LIBRARY Qt6::Core LOCATION)
   get_filename_component(LIB_PATH ${QT_CORE_LIBRARY} PATH)
   get_filename_component(LIB_EXT ${QT_CORE_LIBRARY} EXT)
 
@@ -148,7 +153,7 @@ if(UNIX AND NOT APPLE)
       WORLD_READ
       WORLD_EXECUTE
     COMPONENT ${GITTYUP_NAME}
-    RENAME ${LIB_NAME}.so.5)
+    RENAME ${LIB_NAME}.so.6)
 endif()
 
 # Install SSL libraries.
@@ -156,12 +161,12 @@ if(NOT APPLE)
   if(NOT USE_SYSTEM_OPENSSL)
     if(WIN32)
       if(CMAKE_SIZEOF_VOID_P EQUAL 8)
-        set(SSL_LIB_SUFFIX "-1_1-x64.dll")
+        set(SSL_LIB_SUFFIX "-3-x64.dll")
       else()
-        set(SSL_LIB_SUFFIX "-1_1.dll")
+        set(SSL_LIB_SUFFIX "-3.dll")
       endif()
     else()
-      set(SSL_LIB_SUFFIX ".so.1.1")
+      set(SSL_LIB_SUFFIX ".so.3")
     endif()
 
     foreach(SSL_LIB_NAME ssl crypto)
diff --git a/src/app/Application.cpp b/src/app/Application.cpp
index fc948333a..dac82df53 100644
--- a/src/app/Application.cpp
+++ b/src/app/Application.cpp
@@ -63,19 +63,20 @@ static LONG WINAPI exceptionFilter(PEXCEPTION_POINTERS info) {
   SYSTEMTIME localTime;
   GetLocalTime(&localTime);
 
-  char temp[MAX_PATH];
+  wchar_t temp[MAX_PATH];
   GetTempPath(MAX_PATH, temp);
 
-  char dir[MAX_PATH];
-  StringCchPrintf(dir, MAX_PATH, "%sGittyup", temp);
+  wchar_t dir[MAX_PATH];
+  const wchar_t *gittyup_name = L"%sGittyup";
+  StringCchPrintf(dir, MAX_PATH, gittyup_name, temp);
   CreateDirectory(dir, NULL);
 
-  char fileName[MAX_PATH];
-  StringCchPrintf(
-      fileName, MAX_PATH, "%s\\%s-%s-%04d%02d%02d-%02d%02d%02d-%ld-%ld.dmp",
-      dir, GITTYUP_NAME, GITTYUP_VERSION, localTime.wYear, localTime.wMonth,
-      localTime.wDay, localTime.wHour, localTime.wMinute, localTime.wSecond,
-      GetCurrentProcessId(), GetCurrentThreadId());
+  wchar_t fileName[MAX_PATH];
+  const wchar_t *s = L"%s\\%s-%s-%04d%02d%02d-%02d%02d%02d-%ld-%ld.dmp";
+  StringCchPrintf(fileName, MAX_PATH, s, dir, GITTYUP_NAME, GITTYUP_VERSION,
+                  localTime.wYear, localTime.wMonth, localTime.wDay,
+                  localTime.wHour, localTime.wMinute, localTime.wSecond,
+                  GetCurrentProcessId(), GetCurrentThreadId());
 
   HANDLE dumpFile =
       CreateFile(fileName, GENERIC_READ | GENERIC_WRITE,
@@ -359,7 +360,7 @@ class CopyDataWindow : public QWindow {
 
 protected:
   virtual bool nativeEvent(const QByteArray &eventType, void *message,
-                           long *result) Q_DECL_OVERRIDE {
+                           qintptr *result) Q_DECL_OVERRIDE {
     MSG *msg = (MSG *)message;
 
     if (msg->message == WM_COPYDATA) {
diff --git a/src/app/CMakeLists.txt b/src/app/CMakeLists.txt
index 82bdc3331..46def17fd 100755
--- a/src/app/CMakeLists.txt
+++ b/src/app/CMakeLists.txt
@@ -22,7 +22,7 @@ file(GLOB SCINTILLUA_LEXERS ${SRC_SCINTILLUA_LEXERS_DIR}/*.lua)
 file(GLOB LUA_PLUGINS ${CONF_DIR}/plugins/*.lua ${CONF_DIR}/plugins/*.txt)
 
 # Build resources.
-qt5_add_resources(RESOURCES ${RSRC_DIR}/resources.qrc)
+qt6_add_resources(RESOURCES ${RSRC_DIR}/resources.qrc)
 
 # Generate acknowledgments.
 set(DOC_SOURCE_DIR ${CMAKE_SOURCE_DIR}/docs)
@@ -74,12 +74,12 @@ target_link_libraries(
   git
   ui
   update
-  Qt5::Widgets)
+  Qt6::Widgets)
 
 set_target_properties(app PROPERTIES AUTOMOC ON)
 
 if(UNIX AND NOT APPLE)
-  target_link_libraries(app Qt5::DBus)
+  target_link_libraries(app Qt6::DBus)
 endif()
 
 # Add main executable.
@@ -171,7 +171,7 @@ install(
   COMPONENT ${GITTYUP_NAME})
 
 if(APPLE)
-  get_target_property(QT_LIBRARY Qt5::Core LOCATION)
+  get_target_property(QT_LIBRARY Qt6::Core LOCATION)
   get_filename_component(QT_FRAMEWORK ${QT_LIBRARY} DIRECTORY)
   get_filename_component(RPATH ${QT_FRAMEWORK} DIRECTORY)
 
diff --git a/src/app/CustomTheme.cpp b/src/app/CustomTheme.cpp
index b23138d51..c4ec31c71 100644
--- a/src/app/CustomTheme.cpp
+++ b/src/app/CustomTheme.cpp
@@ -15,6 +15,7 @@
 #include <QProxyStyle>
 #include <QStandardPaths>
 #include <QStyleOptionButton>
+#include <stdexcept>
 
 namespace {
 
diff --git a/src/app/CustomTheme_mac.mm b/src/app/CustomTheme_mac.mm
index 46983231a..46e250d8f 100644
--- a/src/app/CustomTheme_mac.mm
+++ b/src/app/CustomTheme_mac.mm
@@ -25,7 +25,7 @@
   if (color.lightnessF() < 0.5)
     win.appearance = [NSAppearance appearanceNamed:NSAppearanceNameVibrantDark];
 
-  qreal r,g,b,a;
+  float r,g,b,a;
   color.getRgbF(&r,&g,&b,&a);
   win.backgroundColor = [NSColor colorWithDeviceRed:r green:g blue:b alpha:a];
 }
diff --git a/src/app/Gittyup.cpp b/src/app/Gittyup.cpp
index 69649f8c2..5238195e7 100644
--- a/src/app/Gittyup.cpp
+++ b/src/app/Gittyup.cpp
@@ -13,8 +13,6 @@
 #include <QMessageBox>
 
 int main(int argc, char *argv[]) {
-  Application::setAttribute(Qt::AA_EnableHighDpiScaling);
-  Application::setAttribute(Qt::AA_UseHighDpiPixmaps);
   Application app(argc, argv, true);
 
   // Check if only one running instance is allowed and already running
diff --git a/src/app/Theme.cpp b/src/app/Theme.cpp
index 628842462..b677c3084 100644
--- a/src/app/Theme.cpp
+++ b/src/app/Theme.cpp
@@ -17,6 +17,7 @@
 #include <QProxyStyle>
 #include <QStyleOption>
 #include <QWidget>
+#include <stdexcept>
 
 namespace {
 
diff --git a/src/cli/CMakeLists.txt b/src/cli/CMakeLists.txt
index 74dcd7e16..156fc39bf 100644
--- a/src/cli/CMakeLists.txt
+++ b/src/cli/CMakeLists.txt
@@ -7,4 +7,4 @@ endif()
 
 add_library(cli Installer.cpp ${INSTALLER_IMPL_FILE})
 
-target_link_libraries(cli Qt5::Core ${INSTALLER_IMPL_LIBS})
+target_link_libraries(cli Qt6::Core ${INSTALLER_IMPL_LIBS})
diff --git a/src/conf/CMakeLists.txt b/src/conf/CMakeLists.txt
index bbb0f2ce2..e3e06f2cc 100644
--- a/src/conf/CMakeLists.txt
+++ b/src/conf/CMakeLists.txt
@@ -1,7 +1,7 @@
 add_library(conf ConfFile.cpp Settings.cpp Setting.cpp RecentRepositories.cpp
                  RecentRepository.cpp)
 
-target_link_libraries(conf lua Qt5::Core util translation)
+target_link_libraries(conf lua Qt6::Core util translation)
 
 # SRC_ definitions point to the source directly
 target_compile_definitions(
diff --git a/src/conf/Settings.cpp b/src/conf/Settings.cpp
index f3a6ff440..ccd84780f 100644
--- a/src/conf/Settings.cpp
+++ b/src/conf/Settings.cpp
@@ -9,13 +9,14 @@
 
 #include "Settings.h"
 #include "ConfFile.h"
-#include "Debug.h"
 #include "qtsupport.h"
 #include "languages.h"
 #include <QCoreApplication>
 #include <QDir>
+#include <QRegularExpression>
 #include <QSettings>
 #include <QStandardPaths>
+#include <stdexcept>
 
 #ifdef Q_OS_WIN
 #define CS Qt::CaseInsensitive
@@ -125,8 +126,9 @@ QString Settings::lexer(const QString &filename) {
     QVariantMap map(lexers.value(key).toMap());
     if (map.contains("patterns")) {
       foreach (QString pattern, map.value("patterns").toString().split(",")) {
-        QRegExp regExp(pattern, CS, QRegExp::Wildcard);
-        if (regExp.exactMatch(name))
+        QRegularExpression regExp{
+            QRegularExpression::fromWildcard(pattern, CS)};
+        if (regExp.match(name).hasMatch())
           return key;
       }
     }
diff --git a/src/cred/CMakeLists.txt b/src/cred/CMakeLists.txt
index e3516b2a6..b4fe01a7d 100644
--- a/src/cred/CMakeLists.txt
+++ b/src/cred/CMakeLists.txt
@@ -1,5 +1,5 @@
 add_library(cred Cache.cpp Store.cpp CredentialHelper.cpp GitCredential.cpp)
 
-target_link_libraries(cred conf git Qt5::Core)
+target_link_libraries(cred conf git Qt6::Core)
 
 set_target_properties(cred PROPERTIES AUTOMOC ON)
diff --git a/src/dialogs/AmendDialog.h b/src/dialogs/AmendDialog.h
index 670be074f..10e6f846e 100644
--- a/src/dialogs/AmendDialog.h
+++ b/src/dialogs/AmendDialog.h
@@ -26,6 +26,7 @@ struct AmendInfo {
 };
 
 class AmendDialog : public QDialog {
+  Q_OBJECT
 public:
   AmendDialog(const git::Signature &author, const git::Signature &committer,
               const QString &commitMessage, QWidget *parent = nullptr);
diff --git a/src/dialogs/CMakeLists.txt b/src/dialogs/CMakeLists.txt
index 0295257e2..f306af706 100644
--- a/src/dialogs/CMakeLists.txt
+++ b/src/dialogs/CMakeLists.txt
@@ -46,6 +46,6 @@ target_link_libraries(
   cred
   host
   index
-  Qt5::Widgets)
+  Qt6::Widgets)
 
 set_target_properties(dialogs PROPERTIES AUTOMOC ON)
diff --git a/src/dialogs/ConfigDialog.cpp b/src/dialogs/ConfigDialog.cpp
index 7327532f2..a1844c109 100644
--- a/src/dialogs/ConfigDialog.cpp
+++ b/src/dialogs/ConfigDialog.cpp
@@ -30,6 +30,7 @@
 #include "ui/MainWindow.h"
 #include "ui/RepoView.h"
 #include <QAction>
+#include <QActionGroup>
 #include <QCheckBox>
 #include <QDialogButtonBox>
 #include <QFormLayout>
@@ -506,7 +507,7 @@ class LfsPanel : public QWidget {
               watcher->deleteLater();
             });
 
-    watcher->setFuture(QtConcurrent::run(repo, &git::Repository::lfsTracked));
+    watcher->setFuture(QtConcurrent::run(&git::Repository::lfsTracked, repo));
 
     Footer *footer = new Footer(includedList);
     connect(footer, &Footer::plusClicked, this,
diff --git a/src/dialogs/DeleteBranchDialog.cpp b/src/dialogs/DeleteBranchDialog.cpp
index 20741b0c3..4c2e4c49b 100644
--- a/src/dialogs/DeleteBranchDialog.cpp
+++ b/src/dialogs/DeleteBranchDialog.cpp
@@ -61,8 +61,9 @@ DeleteBranchDialog::DeleteBranchDialog(const git::Branch &branch,
 
       entry->setBusy(true);
       QStringList refspecs(QString(":%1").arg(upstreamName));
-      watcher->setFuture(
-          QtConcurrent::run(remote, &git::Remote::push, callbacks, refspecs));
+      git::Result (git::Remote::*push)(
+          git::Remote::Callbacks *, const QStringList &) = &git::Remote::push;
+      watcher->setFuture(QtConcurrent::run(push, remote, callbacks, refspecs));
 
       connect(watcher, &QFutureWatcher<git::Result>::finished, watcher,
               [entry, watcher, callbacks, remoteName] {
diff --git a/src/dialogs/DeleteTagDialog.cpp b/src/dialogs/DeleteTagDialog.cpp
index cd0db7af9..45b1e2be6 100644
--- a/src/dialogs/DeleteTagDialog.cpp
+++ b/src/dialogs/DeleteTagDialog.cpp
@@ -53,8 +53,9 @@ DeleteTagDialog::DeleteTagDialog(const git::TagRef &tag, QWidget *parent)
 
       entry->setBusy(true);
       QStringList refspecs(QString(":refs/tags/%1").arg(name));
-      watcher->setFuture(
-          QtConcurrent::run(remote, &git::Remote::push, callbacks, refspecs));
+      git::Result (git::Remote::*push)(
+          git::Remote::Callbacks *, const QStringList &) = &git::Remote::push;
+      watcher->setFuture(QtConcurrent::run(push, remote, callbacks, refspecs));
 
       connect(watcher, &QFutureWatcher<git::Result>::finished, watcher,
               [entry, watcher, callbacks, remoteName] {
diff --git a/src/dialogs/DiffPanel.cpp b/src/dialogs/DiffPanel.cpp
index 40ad124c7..c8cf46a0e 100644
--- a/src/dialogs/DiffPanel.cpp
+++ b/src/dialogs/DiffPanel.cpp
@@ -21,7 +21,6 @@
 #include <QHBoxLayout>
 #include <QPushButton>
 #include <QSpinBox>
-#include <QTextCodec>
 
 DiffPanel::DiffPanel(const git::Repository &repo, QWidget *parent)
     : QWidget(parent),
@@ -45,12 +44,18 @@ DiffPanel::DiffPanel(const git::Repository &repo, QWidget *parent)
   });
 
   // encoding
+
+  static std::array encodings{
+      "Utf8",  "Utf16",   "Utf16LE", "Utf16BE",
+      "Utf32", "Utf32LE", "Utf32BE", "Latin1",
+  };
+
   QComboBox *encoding = new QComboBox(this);
   encoding->addItem(tr("System Locale"), -1);
   encoding->insertSeparator(encoding->count());
-  foreach (int mib, QTextCodec::availableMibs())
-    encoding->addItem(QTextCodec::codecForMib(mib)->name(), mib);
-
+  for (int i = 0; i < encodings.size(); i++) {
+    encoding->addItem(encodings[i], i);
+  }
   QString name = mConfig.value<QString>("gui.encoding");
   if (!name.isEmpty())
     encoding->setCurrentIndex(encoding->findText(name));
diff --git a/src/dialogs/IconLabel.cpp b/src/dialogs/IconLabel.cpp
index 6bd33e1f0..ac7d418de 100644
--- a/src/dialogs/IconLabel.cpp
+++ b/src/dialogs/IconLabel.cpp
@@ -22,8 +22,7 @@ QSize IconLabel::minimumSizeHint() const { return sizeHint(); }
 
 void IconLabel::paintEvent(QPaintEvent *event) {
   QSize size = sizeHint();
-  QWidget *win = window();
   QPainter(this).drawPixmap(
       QStyle::alignedRect(Qt::LeftToRight, Qt::AlignHCenter, size, rect()),
-      mIcon.pixmap(win ? win->windowHandle() : nullptr, size));
+      mIcon.pixmap(size, window()->devicePixelRatio()));
 }
diff --git a/src/dialogs/SettingsDialog.cpp b/src/dialogs/SettingsDialog.cpp
index 7dfcc3b62..68da02938 100644
--- a/src/dialogs/SettingsDialog.cpp
+++ b/src/dialogs/SettingsDialog.cpp
@@ -28,6 +28,7 @@
 #include "languages.h"
 #include "update/Updater.h"
 #include <QAction>
+#include <QActionGroup>
 #include <QApplication>
 #include <QCheckBox>
 #include <QComboBox>
diff --git a/src/editor/PlatQt.cpp b/src/editor/PlatQt.cpp
index e054f5cec..630acfab5 100644
--- a/src/editor/PlatQt.cpp
+++ b/src/editor/PlatQt.cpp
@@ -329,7 +329,7 @@ void SurfaceImpl::MeasureWidths(Font &font, std::string_view s,
 
 XYPOSITION SurfaceImpl::WidthText(Font &font, std::string_view s) {
   QFontMetricsF metrics(*static_cast<QFont *>(font.GetID()), device);
-  return metrics.width(QString::fromUtf8(s.data(), s.length()));
+  return metrics.horizontalAdvance(QString::fromUtf8(s.data(), s.length()));
 }
 
 XYPOSITION SurfaceImpl::Ascent(Font &font) {
@@ -629,14 +629,15 @@ void Platform::DebugPrintf(const char *format, ...) {
   char buffer[2000];
   va_list pArguments;
   va_start(pArguments, format);
-  vsprintf(buffer, format, pArguments);
+  vsnprintf(buffer, sizeof(buffer), format, pArguments);
   va_end(pArguments);
   Platform::DebugDisplay(buffer);
 }
 
 void Platform::Assert(const char *c, const char *file, int line) {
   char buffer[2000];
-  sprintf(buffer, "Assertion [%s] failed at %s %d\n", c, file, line);
+  snprintf(buffer, sizeof(buffer), "Assertion [%s] failed at %s %d\n", c, file,
+           line);
   Platform::DebugDisplay(buffer);
 }
 
diff --git a/src/editor/ScintillaQt.cpp b/src/editor/ScintillaQt.cpp
index 5df0cc9f9..1ced345a8 100644
--- a/src/editor/ScintillaQt.cpp
+++ b/src/editor/ScintillaQt.cpp
@@ -327,7 +327,9 @@ void ScintillaQt::keyPressEvent(QKeyEvent *event) {
 
     QString text = event->text();
     if (input && !text.isEmpty() && text[0].isPrint()) {
-      InsertCharacter(text.toStdString(), CharacterSource::directInput);
+      QByteArray utext = text.toUtf8();
+      InsertCharacter(std::string_view(utext.data(), utext.size()),
+                      CharacterSource::directInput);
     } else {
       event->ignore();
     }
@@ -430,7 +432,7 @@ void ScintillaQt::dragEnterEvent(QDragEnterEvent *event) {
   if (event->mimeData()->hasText()) {
     event->acceptProposedAction();
 
-    Point point = PointFromQPoint(event->pos());
+    Point point = PointFromQPoint(event->position().toPoint());
     SetDragPosition(
         SPositionFromLocation(point, false, false, UserVirtualSpace()));
   } else {
@@ -447,7 +449,7 @@ void ScintillaQt::dragMoveEvent(QDragMoveEvent *event) {
   if (event->mimeData()->hasText()) {
     event->acceptProposedAction();
 
-    Point point = PointFromQPoint(event->pos());
+    Point point = PointFromQPoint(event->position().toPoint());
     SetDragPosition(
         SPositionFromLocation(point, false, false, UserVirtualSpace()));
   } else {
@@ -460,7 +462,7 @@ void ScintillaQt::dropEvent(QDropEvent *event) {
     event->acceptProposedAction();
 
     const QMimeData *data = event->mimeData();
-    Point point = PointFromQPoint(event->pos());
+    Point point = PointFromQPoint(event->position().toPoint());
     bool move =
         (event->source() == this && event->proposedAction() == Qt::MoveAction);
 
@@ -520,8 +522,9 @@ void ScintillaQt::inputMethodEvent(QInputMethodEvent *event) {
       const unsigned int ucWidth = commitStr.at(i).isHighSurrogate() ? 2 : 1;
       const QString oneCharUTF16 = commitStr.mid(i, ucWidth);
       const QByteArray oneChar = oneCharUTF16.toUtf8();
-
-      InsertCharacter(oneChar.toStdString(), CharacterSource::directInput);
+      const int oneCharLen = oneChar.length();
+      InsertCharacter(std::string_view(oneChar.data(), oneCharLen),
+                      CharacterSource::directInput);
       i += ucWidth;
     }
 
@@ -604,7 +607,8 @@ void ScintillaQt::inputMethodEvent(QInputMethodEvent *event) {
       numBytes += oneCharLen;
       imeCharPos[i + 1] = numBytes;
 
-      InsertCharacter(oneChar.toStdString(), CharacterSource::directInput);
+      InsertCharacter(std::string_view(oneChar.data(), oneCharLen),
+                      CharacterSource::directInput);
 
 #ifdef Q_OS_LINUX
       // Segment marked with imeCaretPos is for target input.
@@ -628,7 +632,7 @@ void ScintillaQt::inputMethodEvent(QInputMethodEvent *event) {
       MoveImeCarets(-imeCharPos[preeditStrLen] + imeCharPos[imeCaretPos]);
     }
 
-    // Set candidate box position for Qt::ImMicroFocus.
+    // Set candidate box position for Qt::ImCursorRectangle.
     preeditPos = CurrentPosition();
     EnsureCaretVisible();
     updateMicroFocus();
@@ -704,6 +708,7 @@ QVariant ScintillaQt::inputMethodQuery(Qt::InputMethodQuery query) const {
     case Qt::ImPlatformData:           // fall through
     case Qt::ImQueryInput:             // fall through
     case Qt::ImQueryAll:               // fall through
+    case Qt::ImReadOnly:               // fall through
       break;
   }
   return QVariant();
@@ -1021,7 +1026,7 @@ bool ScintillaQt::SetIdle(bool on) {
       idler.state = false;
       QTimer *timer = static_cast<QTimer *>(idler.idlerID);
       timer->stop();
-      disconnect(timer, &QTimer::timeout, 0, 0);
+      disconnect(timer, &QTimer::timeout, nullptr, nullptr);
       delete timer;
       idler.idlerID = nullptr;
     }
diff --git a/src/git/CMakeLists.txt b/src/git/CMakeLists.txt
index c9553149b..479eae927 100644
--- a/src/git/CMakeLists.txt
+++ b/src/git/CMakeLists.txt
@@ -27,6 +27,6 @@ add_library(
   TagRef.cpp
   Tree.cpp)
 
-target_link_libraries(git git2 Qt5::Core Qt5::Network util)
+target_link_libraries(git git2 Qt6::Core Qt6::Network util)
 
 set_target_properties(git PROPERTIES AUTOMOC ON)
diff --git a/src/git/Commit.cpp b/src/git/Commit.cpp
index 1cdae15f1..b051d9a48 100644
--- a/src/git/Commit.cpp
+++ b/src/git/Commit.cpp
@@ -26,7 +26,8 @@
 #include <QJsonDocument>
 #include <QJsonObject>
 #include <QRegularExpression>
-#include <QTextCodec>
+#include <QStringConverter>
+#include <QStringDecoder>
 #include <QVector>
 
 namespace git {
@@ -294,8 +295,9 @@ void Commit::setStarred(bool starred) {
 
 QString Commit::decodeMessage(const char *msg) const {
   if (const char *encoding = git_commit_message_encoding(*this)) {
-    if (QTextCodec *codec = QTextCodec::codecForName(encoding))
-      return codec->toUnicode(msg);
+    auto conv = QStringConverter::encodingForName(encoding);
+    if (conv.has_value())
+      return QStringDecoder{conv.value()}.decode(msg);
   }
 
   return msg;
diff --git a/src/git/Commit.h b/src/git/Commit.h
index 11c73a1c5..adae4fb15 100644
--- a/src/git/Commit.h
+++ b/src/git/Commit.h
@@ -15,6 +15,7 @@
 #include "git2/revwalk.h"
 #include "git2/reset.h"
 #include "Blob.h"
+#include <QStringList>
 
 class QDateTime;
 
diff --git a/src/git/Diff.cpp b/src/git/Diff.cpp
index a85ae545d..2497aa82f 100644
--- a/src/git/Diff.cpp
+++ b/src/git/Diff.cpp
@@ -12,14 +12,15 @@
 #include "Debug.h"
 #include "git2/patch.h"
 #include <algorithm>
+#include <stdexcept>
 
 bool containsPath(QString &str, QString &occurence, Qt::CaseSensitivity cs) {
   if (str.contains(occurence, cs)) {
-    if (str.count() == occurence.count()) {
+    if (str.size() == occurence.size()) {
       // file/folder matches exactly
       return true;
-    } else if (str.count() >= occurence.length() + 1 &&
-               str[occurence.length()] == "/") {
+    } else if (str.size() >= occurence.length() + 1 &&
+               str[occurence.length()] == '/') {
       // file or folder in occurence
       return true;
     }
diff --git a/src/git/Diff.h b/src/git/Diff.h
index d1f7d278a..042b06156 100644
--- a/src/git/Diff.h
+++ b/src/git/Diff.h
@@ -59,7 +59,7 @@ class Diff {
    * \return
    */
   QByteArray print();
-  bool isValid() const { return d; }
+  bool isValid() const { return d ? true : false; }
   explicit operator bool() const { return isValid(); }
 
   bool isConflicted() const;
diff --git a/src/git/Index.cpp b/src/git/Index.cpp
index b80b81870..95cd8926e 100644
--- a/src/git/Index.cpp
+++ b/src/git/Index.cpp
@@ -180,7 +180,7 @@ void Index::setStaged(const QStringList &files, bool staged, bool yieldFocus) {
           if (!smHead.isValid())
             continue;
 
-          git_time_t time = smHead.committer().date().toTime_t();
+          git_time_t time = smHead.committer().date().toSecsSinceEpoch();
           entry.ctime.seconds = time;
           entry.ctime.nanoseconds = 0;
           entry.mtime.seconds = time;
diff --git a/src/git/Remote.cpp b/src/git/Remote.cpp
index dfd1013ba..fd5f0b9cf 100644
--- a/src/git/Remote.cpp
+++ b/src/git/Remote.cpp
@@ -175,8 +175,9 @@ class ConfigFile {
         bool matched = false;
 
         for (const QString &pattern : host.patterns) {
-          QRegExp re(pattern, Qt::CaseSensitive, QRegExp::Wildcard);
-          if (re.exactMatch(hostname)) {
+          QRegularExpression re{
+              QRegularExpression::wildcardToRegularExpression(pattern)};
+          if (re.match(hostname).hasMatch()) {
             handler(host);
             matched = true;
             break;
diff --git a/src/git/Repository.cpp b/src/git/Repository.cpp
index d7f91016f..ff0a799c9 100644
--- a/src/git/Repository.cpp
+++ b/src/git/Repository.cpp
@@ -51,7 +51,6 @@
 #include <QProcess>
 #include <QSaveFile>
 #include <QStandardPaths>
-#include <QTextCodec>
 #include <QVector>
 
 #ifdef Q_OS_UNIX
@@ -1032,14 +1031,14 @@ void Repository::cleanupState() {
   }
 }
 
-QTextCodec *Repository::codec() const {
+QStringConverter::Encoding Repository::encoding() const {
   QString encoding = gitConfig().value<QString>("gui.encoding");
-  QTextCodec *codec = QTextCodec::codecForName(encoding.toUtf8());
-  return codec ? codec : QTextCodec::codecForLocale();
+  auto conv = QStringConverter::encodingForName(encoding.toLocal8Bit().data());
+  return conv ? conv.value() : QStringConverter::System;
 }
 
 QString Repository::decode(const QByteArray &text) const {
-  return codec()->toUnicode(text);
+  return QStringDecoder{encoding()}.decode(text);
 }
 
 bool Repository::lfsIsInitialized() { return dir().exists("hooks/pre-push"); }
diff --git a/src/git/Repository.h b/src/git/Repository.h
index 0abb27794..8b9b65afe 100644
--- a/src/git/Repository.h
+++ b/src/git/Repository.h
@@ -26,6 +26,7 @@
 #include <QObject>
 #include <QSet>
 #include <QSharedPointer>
+#include <QStringConverter>
 
 struct git_repository;
 class QProcess;
@@ -225,7 +226,7 @@ class Repository {
   void cleanupState();
 
   // encoding
-  QTextCodec *codec() const;
+  QStringConverter::Encoding encoding() const;
   QString decode(const QByteArray &text) const;
 
   // clean
diff --git a/src/git/Signature.cpp b/src/git/Signature.cpp
index 55cace9ef..e366de228 100644
--- a/src/git/Signature.cpp
+++ b/src/git/Signature.cpp
@@ -42,7 +42,7 @@ QString Signature::email() const { return d->email; }
 
 QDateTime Signature::date() const {
   int offset = d->when.offset * 60; // Convert from minutes to seconds.
-  return QDateTime::fromTime_t(d->when.time, Qt::OffsetFromUTC, offset);
+  return QDateTime::fromSecsSinceEpoch(d->when.time, Qt::OffsetFromUTC, offset);
 }
 
 git_time Signature::gitDate() const { return d->when; }
diff --git a/src/git/Signature.h b/src/git/Signature.h
index c3a516e0c..2f916923d 100644
--- a/src/git/Signature.h
+++ b/src/git/Signature.h
@@ -21,7 +21,7 @@ namespace git {
 
 class Signature {
 public:
-  bool isValid() const { return d; }
+  bool isValid() const { return d ? true : false; }
   explicit operator bool() const { return isValid(); }
 
   QString name() const;
diff --git a/src/host/Account.cpp b/src/host/Account.cpp
index 0e2af7030..1abbac572 100644
--- a/src/host/Account.cpp
+++ b/src/host/Account.cpp
@@ -21,6 +21,7 @@
 #include <QPalette>
 #include <QSettings>
 #include <qnetworkaccessmanager.h>
+#include <stdexcept>
 
 namespace {
 
diff --git a/src/host/CMakeLists.txt b/src/host/CMakeLists.txt
index 027107356..d189c0aa6 100644
--- a/src/host/CMakeLists.txt
+++ b/src/host/CMakeLists.txt
@@ -9,7 +9,7 @@ add_library(
   GitLab.cpp
   Repository.cpp)
 
-target_link_libraries(host conf cred Qt5::Core Qt5::Gui Qt5::Network)
+target_link_libraries(host conf cred Qt6::Core Qt6::Gui Qt6::Network)
 
 target_compile_definitions(
   host
diff --git a/src/host/Repository.h b/src/host/Repository.h
index 02f389baf..b6011f67a 100644
--- a/src/host/Repository.h
+++ b/src/host/Repository.h
@@ -10,6 +10,7 @@
 #ifndef HOST_REPOSITORY_H
 #define HOST_REPOSITORY_H
 
+#include <QObject>
 #include <QMap>
 #include <QMetaType>
 #include <QSharedPointer>
diff --git a/src/index/CMakeLists.txt b/src/index/CMakeLists.txt
index 26b911754..0fe9b1452 100644
--- a/src/index/CMakeLists.txt
+++ b/src/index/CMakeLists.txt
@@ -7,8 +7,8 @@ target_link_libraries(
   git
   lpeg
   lua
-  Qt5::Core
-  Qt5::Concurrent)
+  Qt6::Core
+  Qt6::Concurrent)
 
 set_target_properties(index PROPERTIES AUTOMOC ON)
 
@@ -16,7 +16,7 @@ add_executable(lexer_test lexer_test.cpp)
 target_link_libraries(lexer_test index)
 
 add_executable(index_test index_test.cpp)
-target_link_libraries(index_test index Qt5::Widgets)
+target_link_libraries(index_test index Qt6::Widgets)
 
 add_executable(indexer indexer.cpp)
 target_link_libraries(indexer index)
diff --git a/src/index/Index.cpp b/src/index/Index.cpp
index d48ad5d8d..d448b2db2 100644
--- a/src/index/Index.cpp
+++ b/src/index/Index.cpp
@@ -22,6 +22,8 @@
 #include <QSettings>
 #include <QtConcurrent>
 
+#include <stdexcept>
+
 namespace {
 
 const QString kLogKey = "debug/indexer";
diff --git a/src/index/Query.cpp b/src/index/Query.cpp
index 11d143085..c293a8b0d 100644
--- a/src/index/Query.cpp
+++ b/src/index/Query.cpp
@@ -12,7 +12,7 @@
 #include <QDate>
 #include <QMap>
 #include <QSet>
-#include <QRegExp>
+#include <QRegularExpression>
 
 namespace {
 
@@ -89,9 +89,10 @@ class WildcardQuery : public TermQuery {
   WildcardQuery(const Index::Term &term) : TermQuery(term) {}
 
   QList<git::Commit> commits(const Index *index) const override {
-    QRegExp re(mTerm.text, Qt::CaseInsensitive, QRegExp::Wildcard);
+    QRegularExpression re{
+        QRegularExpression::fromWildcard(mTerm.text, Qt::CaseInsensitive)};
     Index::Predicate pred = [re](const QByteArray &word) {
-      return re.exactMatch(word);
+      return re.match(word).hasMatch();
     };
 
     return index->commits(index->postings(pred, mTerm.field));
@@ -182,24 +183,16 @@ class BooleanQuery : public Query {
     QList<git::Commit> rhs = mRhs->commits(index);
     QList<git::Commit> commits = mLhs->commits(index);
     if (mKind == And) {
-// Remove commits that don't match the right hand side.
-#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+      // Remove commits that don't match the right hand side.
       QSet<git::Commit> set(rhs.begin(), rhs.end());
-#else
-      QSet<git::Commit> set = QSet<git::Commit>::fromList(rhs);
-#endif
       QMutableListIterator<git::Commit> it(commits);
       while (it.hasNext()) {
         if (!set.contains(it.next()))
           it.remove();
       }
     } else {
-// Add commits that aren't already in the result set.
-#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+      // Add commits that aren't already in the result set.
       QSet<git::Commit> set(commits.begin(), commits.end());
-#else
-      QSet<git::Commit> set = QSet<git::Commit>::fromList(commits);
-#endif
       foreach (const git::Commit &commit, rhs) {
         if (!set.contains(commit))
           commits.append(commit);
@@ -222,9 +215,10 @@ class PathspecQuery : public TermQuery {
   QList<git::Commit> commits(const Index *index) const override {
     QByteArray term = mTerm.text.toUtf8();
     QByteArray prefix = term.endsWith('/') ? term : term + '/';
-    QRegExp re(mTerm.text, Qt::CaseInsensitive, QRegExp::Wildcard);
+    QRegularExpression re{
+        QRegularExpression::fromWildcard(mTerm.text, Qt::CaseInsensitive)};
     Index::Predicate pred = [prefix, re](const QByteArray &word) {
-      return word.startsWith(prefix) || re.exactMatch(word);
+      return word.startsWith(prefix) || re.match(word).hasMatch();
     };
 
     return index->commits(index->postings(pred, Index::Path));
diff --git a/src/index/indexer.cpp b/src/index/indexer.cpp
index b6473a171..78220f10b 100644
--- a/src/index/indexer.cpp
+++ b/src/index/indexer.cpp
@@ -53,19 +53,20 @@ static LONG WINAPI exceptionFilter(PEXCEPTION_POINTERS info) {
   SYSTEMTIME localTime;
   GetLocalTime(&localTime);
 
-  char temp[MAX_PATH];
+  wchar_t temp[MAX_PATH];
   GetTempPath(MAX_PATH, temp);
 
-  char dir[MAX_PATH];
-  StringCchPrintf(dir, MAX_PATH, "%sGittyup", temp);
+  wchar_t dir[MAX_PATH];
+  const wchar_t *gittyup_name = L"%sGittyup";
+  StringCchPrintf(dir, MAX_PATH, gittyup_name, temp);
   CreateDirectory(dir, NULL);
 
-  char fileName[MAX_PATH];
-  StringCchPrintf(
-      fileName, MAX_PATH, "%s\\%s-%s-%04d%02d%02d-%02d%02d%02d-%ld-%ld.dmp",
-      dir, "indexer", GITTYUP_VERSION, localTime.wYear, localTime.wMonth,
-      localTime.wDay, localTime.wHour, localTime.wMinute, localTime.wSecond,
-      GetCurrentProcessId(), GetCurrentThreadId());
+  wchar_t fileName[MAX_PATH];
+  const wchar_t *s = L"%s\\%s-%s-%04d%02d%02d-%02d%02d%02d-%ld-%ld.dmp";
+  StringCchPrintf(fileName, MAX_PATH, s, dir, "indexer", GITTYUP_VERSION,
+                  localTime.wYear, localTime.wMonth, localTime.wDay,
+                  localTime.wHour, localTime.wMinute, localTime.wSecond,
+                  GetCurrentProcessId(), GetCurrentThreadId());
 
   HANDLE dumpFile =
       CreateFile(fileName, GENERIC_READ | GENERIC_WRITE,
@@ -427,12 +428,8 @@ class Indexer : public QObject, public QAbstractNativeEventFilter {
     int count = 0;
     QList<git::Commit> commits;
     git::Commit commit = mWalker.next();
-
-#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
     QSet<git::Id> ids(mIndex.ids().begin(), mIndex.ids().end());
-#else
-    QSet<git::Id> ids = QSet<git::Id>::fromList(mIndex.ids());
-#endif
+
     while (commit.isValid() && count < 8192) {
       // Don't index merge commits.
       if (!commit.isMerge() && !ids.contains(commit.id())) {
@@ -453,7 +450,7 @@ class Indexer : public QObject, public QAbstractNativeEventFilter {
     using CommitList = QList<git::Commit>;
     mWatcher.setFuture(
         QtConcurrent::mappedReduced<Index::PostingMap, CommitList, Map, Reduce>(
-            commits, Map(mIndex.repo(), mLexers, mOut),
+            std::move(commits), Map(mIndex.repo(), mLexers, mOut),
             Reduce(mIndex.ids(), mOut)));
     return true;
   }
@@ -476,7 +473,7 @@ class Indexer : public QObject, public QAbstractNativeEventFilter {
   }
 
   bool nativeEventFilter(const QByteArray &type, void *message,
-                         long *result) override {
+                         qintptr *result) override {
     Q_UNUSED(result);
 #ifdef Q_OS_WIN
     MSG *msg = static_cast<MSG *>(message);
diff --git a/src/log/CMakeLists.txt b/src/log/CMakeLists.txt
index 675c3c2f4..a6d385bbe 100644
--- a/src/log/CMakeLists.txt
+++ b/src/log/CMakeLists.txt
@@ -1,5 +1,5 @@
 add_library(loglib LogDelegate.cpp LogEntry.cpp LogModel.cpp LogView.cpp)
 
-target_link_libraries(loglib Qt5::Widgets)
+target_link_libraries(loglib Qt6::Widgets)
 
 set_target_properties(loglib PROPERTIES AUTOMOC ON)
diff --git a/src/log/LogDelegate.cpp b/src/log/LogDelegate.cpp
index d461a5989..0a3dd2fb5 100644
--- a/src/log/LogDelegate.cpp
+++ b/src/log/LogDelegate.cpp
@@ -78,7 +78,7 @@ void LogDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
     return;
 
   QRect rect = decorationRect(option, index);
-  if (static_cast<QMetaType::Type>(variant.type()) == QMetaType::QChar) {
+  if (variant.typeId() == QMetaType::QChar) {
     Badge::paint(painter,
                  {Badge::Label(Badge::Label::Type::Log, variant.toChar())},
                  rect, &opt);
@@ -127,7 +127,7 @@ void LogDelegate::initStyleOption(QStyleOptionViewItem *option,
                                   const QModelIndex &index) const {
   QStyledItemDelegate::initStyleOption(option, index);
   QVariant variant = index.data(Qt::DecorationRole);
-  if (static_cast<QMetaType::Type>(variant.type()) == QMetaType::QChar) {
+  if (variant.typeId() == QMetaType::QChar) {
     option->decorationSize =
         Badge::size(option->font, Badge::Label(Badge::Label::Type::Log)) -
         ADJUSTMENT_SIZE;
diff --git a/src/log/LogModel.cpp b/src/log/LogModel.cpp
index 66e4c82fd..9bcf9dbd5 100644
--- a/src/log/LogModel.cpp
+++ b/src/log/LogModel.cpp
@@ -11,6 +11,7 @@
 #include "LogEntry.h"
 #include <QLocale>
 #include <QStyle>
+#include <QLocale>
 
 namespace {
 
diff --git a/src/log/LogView.cpp b/src/log/LogView.cpp
index 878611e31..3f1fc99d6 100644
--- a/src/log/LogView.cpp
+++ b/src/log/LogView.cpp
@@ -18,6 +18,7 @@
 #include <QHeaderView>
 #include <QMimeData>
 #include <QMouseEvent>
+#include <QRegularExpression>
 
 namespace {
 
@@ -93,8 +94,8 @@ void LogView::copy() {
       prefix += isExpanded(index) ? "[-]" : "[+]";
 
     QString text = index.data().toString();
-    plainText +=
-        QString("%1 %2\n").arg(prefix, text.remove(QRegExp("<[^>]*>")));
+    plainText += QString("%1 %2\n").arg(
+        prefix, text.remove(QRegularExpression("<[^>]*>")));
     richText += QString("%1 %2<br>").arg(prefix, text);
   }
 
@@ -169,7 +170,8 @@ QString LogView::linkAt(const QModelIndex &index, const QPoint &pos) {
     return QString();
 
   LogDelegate *delegate = static_cast<LogDelegate *>(itemDelegate());
-  QStyleOptionViewItem options = viewOptions();
+  QStyleOptionViewItem options;
+  initViewItemOption(&options);
   options.rect = visualRect(index);
   QPoint docPos = pos - delegate->documentPosition(options, index);
   return delegate->document(index)->documentLayout()->anchorAt(docPos);
@@ -180,7 +182,8 @@ bool LogView::isDecoration(const QModelIndex &index, const QPoint &pos) {
     return false;
 
   LogDelegate *delegate = static_cast<LogDelegate *>(itemDelegate());
-  QStyleOptionViewItem options = viewOptions();
+  QStyleOptionViewItem options;
+  initViewItemOption(&options);
   options.rect = visualRect(index);
   return delegate->decorationRect(options, index).contains(pos);
 }
diff --git a/src/plugins/CMakeLists.txt b/src/plugins/CMakeLists.txt
index a2246fb84..91538b5e8 100644
--- a/src/plugins/CMakeLists.txt
+++ b/src/plugins/CMakeLists.txt
@@ -1,5 +1,5 @@
 add_library(plugins Plugin.cpp)
 
-target_link_libraries(plugins editor git lua Qt5::Core)
+target_link_libraries(plugins editor git lua Qt6::Core)
 
 set_target_properties(plugins PROPERTIES AUTOMOC ON)
diff --git a/src/plugins/Plugin.cpp b/src/plugins/Plugin.cpp
index 54190c1f3..945873dc9 100644
--- a/src/plugins/Plugin.cpp
+++ b/src/plugins/Plugin.cpp
@@ -15,6 +15,8 @@
 #include <QCoreApplication>
 #include <QTextStream>
 
+#include <stdexcept>
+
 extern "C" {
 #include "lua.h"
 #include "lauxlib.h"
diff --git a/src/tools/CMakeLists.txt b/src/tools/CMakeLists.txt
index 6c2dd8055..405ea8543 100644
--- a/src/tools/CMakeLists.txt
+++ b/src/tools/CMakeLists.txt
@@ -1,6 +1,6 @@
 add_library(tools DiffTool.cpp EditTool.cpp ExternalTool.cpp MergeTool.cpp
                   ShowTool.cpp)
 
-target_link_libraries(tools conf git Qt5::Gui util)
+target_link_libraries(tools conf git Qt6::Gui util)
 
 set_target_properties(tools PROPERTIES AUTOMOC ON)
diff --git a/src/tools/DiffTool.cpp b/src/tools/DiffTool.cpp
index 67019a67d..8ae5a01e1 100644
--- a/src/tools/DiffTool.cpp
+++ b/src/tools/DiffTool.cpp
@@ -91,7 +91,7 @@ bool DiffTool::start() {
   if (!bash.isEmpty()) {
     process->start(bash, {"-c", command});
   } else if (!shell) {
-    process->start(git::Command::substitute(env, command));
+    process->start(git::Command::substitute(env, command), QStringList());
   } else {
     emit error(BashNotFound);
     return false;
diff --git a/src/tools/MergeTool.cpp b/src/tools/MergeTool.cpp
index 677f679b2..0c03d9173 100644
--- a/src/tools/MergeTool.cpp
+++ b/src/tools/MergeTool.cpp
@@ -128,7 +128,7 @@ bool MergeTool::start() {
   if (!bash.isEmpty()) {
     process->start(bash, {"-c", command});
   } else if (!shell) {
-    process->start(git::Command::substitute(env, command));
+    process->start(git::Command::substitute(env, command), QStringList());
   } else {
     emit error(BashNotFound);
     return false;
diff --git a/src/ui/AdvancedSearchWidget.cpp b/src/ui/AdvancedSearchWidget.cpp
index a4181ea3f..ad10e269a 100644
--- a/src/ui/AdvancedSearchWidget.cpp
+++ b/src/ui/AdvancedSearchWidget.cpp
@@ -17,7 +17,6 @@
 #include <QScreen>
 #include <QCalendarWidget>
 #include <QComboBox>
-#include <QDesktopWidget>
 #include <QFormLayout>
 #include <QHBoxLayout>
 #include <QLabel>
@@ -144,7 +143,7 @@ void AdvancedSearchWidget::exec(QLineEdit *parent, Index *index) {
   }
 
   // Load completion data in the background.
-  QtConcurrent::run([this, index] {
+  std::ignore = QtConcurrent::run([this, index] {
     QMap<Index::Field, QStringList> fields = index->fieldMap();
     foreach (QLineEdit *lineEdit, mLineEdits) {
       QVariant var = lineEdit->property(kFieldProp);
diff --git a/src/ui/BlameEditor.cpp b/src/ui/BlameEditor.cpp
index e3a610bb4..53275caae 100644
--- a/src/ui/BlameEditor.cpp
+++ b/src/ui/BlameEditor.cpp
@@ -157,7 +157,7 @@ bool BlameEditor::load(const QString &name, const git::Blob &blob,
   // Calculate blame.
   if (mRepo.isValid() && !content.isEmpty()) {
     mMargin->startBlame(name);
-    mBlame.setFuture(QtConcurrent::run(mRepo, &git::Repository::blame, name,
+    mBlame.setFuture(QtConcurrent::run(&git::Repository::blame, mRepo, name,
                                        commit, mCallbacks.data()));
   }
 
@@ -192,8 +192,7 @@ void BlameEditor::save() {
 
   QTextStream out(&file);
   if (mRepo.isValid())
-    out.setCodec(mRepo.codec());
-
+    out.setEncoding(mRepo.encoding());
   out << mEditor->text();
   file.commit();
 
diff --git a/src/ui/BlameMargin.cpp b/src/ui/BlameMargin.cpp
index a8b4ea7ec..5950c2012 100644
--- a/src/ui/BlameMargin.cpp
+++ b/src/ui/BlameMargin.cpp
@@ -67,8 +67,8 @@ void BlameMargin::setBlame(const git::Repository &repo,
           .toBool()) {
     git::Commit first = repo.walker(GIT_SORT_TIME | GIT_SORT_REVERSE).next();
     git::Commit last = repo.walker(GIT_SORT_TIME).next();
-    mMinTime = first ? first.committer().date().toTime_t() : -1;
-    mMaxTime = last ? last.committer().date().toTime_t() : -1;
+    mMinTime = first ? first.committer().date().toSecsSinceEpoch() : -1;
+    mMaxTime = last ? last.committer().date().toSecsSinceEpoch() : -1;
   }
 
   mTimer.stop();
@@ -136,11 +136,12 @@ bool BlameMargin::event(QEvent *event) {
 }
 
 void BlameMargin::mousePressEvent(QMouseEvent *event) {
-  mIndex = mBlame.isValid() ? index(event->y()) : -1;
+  mIndex = mBlame.isValid() ? index(event->position().y()) : -1;
 }
 
 void BlameMargin::mouseReleaseEvent(QMouseEvent *event) {
-  if (mBlame.isValid() && mIndex >= 0 && mIndex == index(event->y())) {
+  if (mBlame.isValid() && mIndex >= 0 &&
+      mIndex == index(event->position().y())) {
     // Update selection.
     git::Id id = mBlame.id(mIndex);
     mSelection = (mSelection != id) ? id : git::Id();
@@ -154,7 +155,7 @@ void BlameMargin::mouseDoubleClickEvent(QMouseEvent *event) {
   if (!mBlame.isValid())
     return;
 
-  int index = this->index(event->y());
+  int index = this->index(event->position().y());
   if (index < 0)
     return;
 
@@ -172,7 +173,7 @@ void BlameMargin::mouseDoubleClickEvent(QMouseEvent *event) {
 void BlameMargin::paintEvent(QPaintEvent *event) {
   // Draw background.
   QStyleOption opt;
-  opt.init(this);
+  opt.initFrom(this);
   QPainter painter(this);
   style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this);
 
@@ -225,7 +226,7 @@ void BlameMargin::paintEvent(QPaintEvent *event) {
       date = (dateTime.date() == today)
                  ? QLocale().toString(dateTime.time(), QLocale::ShortFormat)
                  : QLocale().toString(dateTime.date(), QLocale::ShortFormat);
-      time = dateTime.toTime_t();
+      time = dateTime.toSecsSinceEpoch();
     }
 
     // Draw background.
diff --git a/src/ui/CMakeLists.txt b/src/ui/CMakeLists.txt
index 79d96f803..99b337771 100644
--- a/src/ui/CMakeLists.txt
+++ b/src/ui/CMakeLists.txt
@@ -75,8 +75,8 @@ target_link_libraries(
   tools
   update
   watcher
-  Qt5::Concurrent
-  Qt5::Network
-  Qt5::Widgets)
+  Qt6::Concurrent
+  Qt6::Network
+  Qt6::Widgets)
 
 set_target_properties(ui PROPERTIES AUTOMOC ON)
diff --git a/src/ui/ColumnView.cpp b/src/ui/ColumnView.cpp
index da2da30dd..6d607cdcd 100644
--- a/src/ui/ColumnView.cpp
+++ b/src/ui/ColumnView.cpp
@@ -84,7 +84,8 @@ class PreviewWidget : public QFrame {
 
     QWindow *win = window()->windowHandle();
     QIcon icon = index.data(Qt::DecorationRole).value<QIcon>();
-    mIcon->setPixmap(icon.pixmap(win, QSize(ICON_SIZE, ICON_SIZE)));
+    mIcon->setPixmap(
+        icon.pixmap(QSize(ICON_SIZE, ICON_SIZE), window()->devicePixelRatio()));
 
     mName->setText(kNameFmt.arg(index.data(Qt::DisplayRole).toString()));
 
@@ -139,7 +140,8 @@ void ColumnView::setModel(QAbstractItemModel *model) {
 bool ColumnView::eventFilter(QObject *obj, QEvent *event) {
   if (event->type() == QEvent::MouseButtonPress) {
     QWidget *columnViewport = static_cast<QWidget *>(obj);
-    QPoint globalPos = static_cast<QMouseEvent *>(event)->globalPos();
+    QPoint globalPos =
+        static_cast<QMouseEvent *>(event)->globalPosition().toPoint();
     QModelIndex index = indexAt(viewport()->mapFromGlobal(globalPos));
     if (!columnViewport->hasFocus() && index.row() < 0) {
       columnViewport->setFocus();
diff --git a/src/ui/CommitEditor.cpp b/src/ui/CommitEditor.cpp
index c885c235e..816e2721c 100644
--- a/src/ui/CommitEditor.cpp
+++ b/src/ui/CommitEditor.cpp
@@ -20,6 +20,7 @@
 #include <QVBoxLayout>
 #include <QRegularExpression>
 #include <QRegularExpressionMatch>
+#include <QActionGroup>
 
 namespace {
 const QString kDictKey = "commit.spellcheck.dict";
diff --git a/src/ui/CommitList.cpp b/src/ui/CommitList.cpp
index 4f303a97b..9f17001dd 100644
--- a/src/ui/CommitList.cpp
+++ b/src/ui/CommitList.cpp
@@ -327,6 +327,8 @@ class CommitModel : public QAbstractListModel {
   }
 
   QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const {
+    if (index.row() >= mRows.size())
+      return QVariant();
     const Row &row = mRows.at(index.row());
     bool status = !row.commit.isValid();
     switch (role) {
@@ -1280,8 +1282,10 @@ git::Diff CommitList::selectedDiff() const {
   if (indexes.isEmpty())
     return git::Diff();
 
-  if (indexes.size() == 1)
-    return indexes.first().data(DiffRole).value<git::Diff>();
+  if (indexes.size() == 1) {
+    auto first = indexes.first().data(DiffRole);
+    return first.isValid() ? first.value<git::Diff>() : git::Diff();
+  }
 
   git::Commit first = indexes.first().data(CommitRole).value<git::Commit>();
   if (!first.isValid())
@@ -1863,7 +1867,8 @@ bool CommitList::isDecoration(const QModelIndex &index, const QPoint &pos) {
     return false;
 
   CommitDelegate *delegate = static_cast<CommitDelegate *>(itemDelegate());
-  QStyleOptionViewItem options = viewOptions();
+  QStyleOptionViewItem options;
+  initViewItemOption(&options);
   options.rect = visualRect(index);
   return delegate->decorationRect(options, index).contains(pos);
 }
@@ -1873,7 +1878,8 @@ bool CommitList::isStar(const QModelIndex &index, const QPoint &pos) {
     return false;
 
   CommitDelegate *delegate = static_cast<CommitDelegate *>(itemDelegate());
-  QStyleOptionViewItem options = viewOptions();
+  QStyleOptionViewItem options;
+  initViewItemOption(&options);
   options.rect = visualRect(index);
   return delegate->starRect(options, index).contains(pos);
 }
diff --git a/src/ui/CommitToolBar.cpp b/src/ui/CommitToolBar.cpp
index f4c5178d3..0384b2fe8 100644
--- a/src/ui/CommitToolBar.cpp
+++ b/src/ui/CommitToolBar.cpp
@@ -14,6 +14,7 @@
 #include "ConfigKeys.h"
 #include "conf/Settings.h"
 #include "git/Config.h"
+#include <QActionGroup>
 #include <QApplication>
 #include <QMenu>
 #include <QPainter>
diff --git a/src/ui/DetailView.cpp b/src/ui/DetailView.cpp
index 95b280f12..bb57f1201 100644
--- a/src/ui/DetailView.cpp
+++ b/src/ui/DetailView.cpp
@@ -23,6 +23,7 @@
 #include "git/Signature.h"
 #include <QAbstractTextDocumentLayout>
 #include <QApplication>
+#include <QActionGroup>
 #include <QClipboard>
 #include <QCryptographicHash>
 #include <QDateTime>
@@ -122,8 +123,9 @@ class AuthorCommitterDate : public QWidget {
     mDate = new QLabel(this);
     mDate->setTextInteractionFlags(kTextFlags);
 
-    mSpacing.setX(style()->pixelMetric(QStyle::PM_LayoutHorizontalSpacing));
-    mSpacing.setY(style()->pixelMetric(QStyle::PM_LayoutVerticalSpacing));
+    mHorizontalSpacing =
+        style()->pixelMetric(QStyle::PM_LayoutHorizontalSpacing);
+    mVerticalSpacing = style()->pixelMetric(QStyle::PM_LayoutVerticalSpacing);
   }
 
   void moveEvent(QMoveEvent *event) override { updateLayout(); }
@@ -134,13 +136,13 @@ class AuthorCommitterDate : public QWidget {
     QSize date = mDate->sizeHint();
     QSize author = mAuthor->sizeHint();
     QSize committer = mCommitter->sizeHint();
-    int width = author.width() + date.width() + mSpacing.x();
+    int width = author.width() + date.width() + mHorizontalSpacing;
     int height;
     if (mSameAuthorCommitter)
       height = qMax(qMax(author.height(), committer.height()), date.height());
     else
       height = qMax(author.height(), date.height()) + committer.height() +
-               mSpacing.y();
+               mVerticalSpacing;
     return QSize(width, height);
   }
 
@@ -154,7 +156,7 @@ class AuthorCommitterDate : public QWidget {
       height = qMax(qMax(author.height(), committer.height()), date.height());
     else
       height = qMax(author.height(), date.height()) + committer.height() +
-               mSpacing.y();
+               mVerticalSpacing;
     return QSize(width, height);
   }
 
@@ -165,10 +167,11 @@ class AuthorCommitterDate : public QWidget {
     int author = mAuthor->sizeHint().height();
     int committer = mCommitter->sizeHint().height();
     bool wrapped = (width < sizeHint().width());
-    int unwrappedHeight = mSameAuthorCommitter
-                              ? qMax(committer, qMax(author, date))
-                              : qMax(author + committer + mSpacing.y(), date);
-    return wrapped ? (author + committer + date + 2 * mSpacing.y())
+    int unwrappedHeight =
+        mSameAuthorCommitter
+            ? qMax(committer, qMax(author, date))
+            : qMax(author + committer + mVerticalSpacing, date);
+    return wrapped ? (author + committer + date + 2 * mVerticalSpacing)
                    : unwrappedHeight;
   }
 
@@ -198,13 +201,13 @@ class AuthorCommitterDate : public QWidget {
   void updateLayout() {
     mAuthor->move(0, 0);
     if (mCommitter->isVisible())
-      mCommitter->move(0, mAuthor->height() + mSpacing.y());
+      mCommitter->move(0, mAuthor->height() + mVerticalSpacing);
 
     bool wrapped = (width() < sizeHint().width());
     int x = wrapped ? 0 : width() - mDate->width();
-    int y = wrapped
-                ? mAuthor->height() + mCommitter->height() + 2 * mSpacing.y()
-                : 0;
+    int y = wrapped ? mAuthor->height() + mCommitter->height() +
+                          2 * mVerticalSpacing
+                    : 0;
     mDate->move(x, y);
     updateGeometry();
   }
@@ -213,7 +216,8 @@ class AuthorCommitterDate : public QWidget {
   QLabel *mCommitter;
   QLabel *mDate;
 
-  QPoint mSpacing;
+  int mHorizontalSpacing;
+  int mVerticalSpacing;
   bool mSameAuthorCommitter{false};
 };
 
@@ -306,7 +310,7 @@ class CommitDetail : public QFrame {
     // Compute description asynchronously.
     if (commits.size() == 1)
       mWatcher.setFuture(
-          QtConcurrent::run(commits.first(), &git::Commit::description));
+          QtConcurrent::run(&git::Commit::description, commits.first()));
   }
 
   void setCommits(const QList<git::Commit> &commits) {
diff --git a/src/ui/DiffView/HunkWidget.cpp b/src/ui/DiffView/HunkWidget.cpp
index 24bc5eff4..8224004b2 100644
--- a/src/ui/DiffView/HunkWidget.cpp
+++ b/src/ui/DiffView/HunkWidget.cpp
@@ -281,7 +281,7 @@ HunkWidget::HunkWidget(DiffView *view, const git::Diff &diff,
         return;
 
       QTextStream out(&file);
-      out.setCodec(repo.codec());
+      out.setEncoding(repo.encoding());
       out << editor.text();
       file.commit();
 
@@ -408,7 +408,7 @@ HunkWidget::HunkWidget(DiffView *view, const git::Diff &diff,
                   return;
 
                 QTextStream out(&file);
-                out.setCodec(repo.codec());
+                out.setEncoding(repo.encoding());
                 out << editor.text();
                 file.commit();
 
diff --git a/src/ui/DiffView/Images.cpp b/src/ui/DiffView/Images.cpp
index f3098bb93..c51d4c06d 100644
--- a/src/ui/DiffView/Images.cpp
+++ b/src/ui/DiffView/Images.cpp
@@ -120,7 +120,7 @@ QPixmap Images::loadPixmap(git::Diff::File type, int &size, bool lfs) {
   QFileIconProvider provider;
   QString path = mPatch.repo().workdir().filePath(mPatch.name());
   QIcon icon = provider.icon(QFileInfo(path));
-  return icon.pixmap(windowHandle(), QSize(64, 64));
+  return icon.pixmap(QSize(64, 64), window()->devicePixelRatio());
 }
 
 QVBoxLayout *Images::imageLayout(const QPixmap pixmap, int size) {
diff --git a/src/ui/FindWidget.cpp b/src/ui/FindWidget.cpp
index 2404599b5..e047417c0 100644
--- a/src/ui/FindWidget.cpp
+++ b/src/ui/FindWidget.cpp
@@ -227,7 +227,7 @@ void FindWidget::showAndSetFocus() {
 
 void FindWidget::paintEvent(QPaintEvent *) {
   QStyleOption opt;
-  opt.init(this);
+  opt.initFrom(this);
   QPainter painter(this);
   style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this);
 }
diff --git a/src/ui/MainWindow.cpp b/src/ui/MainWindow.cpp
index 5b6971a90..a5e150ae2 100644
--- a/src/ui/MainWindow.cpp
+++ b/src/ui/MainWindow.cpp
@@ -27,7 +27,6 @@
 #include <QGuiApplication>
 #include <QScreen>
 #include <QCryptographicHash>
-#include <QDesktopWidget>
 #include <QMessageBox>
 #include <QMimeData>
 #include <QSettings>
diff --git a/src/ui/MenuBar.cpp b/src/ui/MenuBar.cpp
index 77c76dae6..89763fe5b 100644
--- a/src/ui/MenuBar.cpp
+++ b/src/ui/MenuBar.cpp
@@ -502,7 +502,7 @@ MenuBar::MenuBar(QWidget *parent) : QMenuBar(parent) {
   mToggleMaximize = new StateAction(tr("Normal"), tr("Maximize"), viewMenu);
   viewMenu->addAction(mToggleMaximize);
   toggleMaximizeHotkey.use(mToggleMaximize);
-  mToggleMaximize->setShortcut(QKeySequence(Qt::CTRL + Qt::Key_M));
+  mToggleMaximize->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_M));
   connect(mToggleMaximize, &QAction::triggered, [this] {
     bool maximize = mToggleMaximize->isActive();
     RepoView *view = this->view();
diff --git a/src/ui/ReferenceView.cpp b/src/ui/ReferenceView.cpp
index 84b3b39df..9cab9739a 100644
--- a/src/ui/ReferenceView.cpp
+++ b/src/ui/ReferenceView.cpp
@@ -40,7 +40,8 @@ class FilterProxyModel : public QSortFilterProxyModel {
   FilterProxyModel(QObject *parent = nullptr) : QSortFilterProxyModel(parent) {}
 
   void setFilter(const QString &filter) {
-    setFilterRegExp(QRegExp(filter, Qt::CaseInsensitive, QRegExp::FixedString));
+    setFilterCaseSensitivity(Qt::CaseSensitivity::CaseInsensitive);
+    setFilterFixedString(filter);
   }
 
 protected:
diff --git a/src/ui/RepoView.cpp b/src/ui/RepoView.cpp
index ff398a5cf..dc6878cdb 100644
--- a/src/ui/RepoView.cpp
+++ b/src/ui/RepoView.cpp
@@ -1806,8 +1806,11 @@ void RepoView::push(const git::Remote &rmt, const git::Reference &src,
           &RepoView::notifyReferenceUpdated);
 
   entry->setBusy(true);
-  mWatcher->setFuture(QtConcurrent::run(remote, &git::Remote::push, mCallbacks,
-                                        ref, dst, force, tags));
+  git::Result (git::Remote::*push)(git::Remote::Callbacks *,
+                                   const git::Reference &, const QString &,
+                                   bool, bool) = &git::Remote::push;
+  mWatcher->setFuture(
+      QtConcurrent::run(push, remote, mCallbacks, ref, dst, force, tags));
 }
 
 bool RepoView::commit(const QString &message,
@@ -2376,7 +2379,7 @@ void RepoView::resetSubmodulesAsync(const QList<SubmoduleInfo> &submodules,
                                    QString(), mWatcher, repo);
 
   entry->setBusy(true);
-  mWatcher->setFuture(QtConcurrent::run(submodule, &git::Submodule::update,
+  mWatcher->setFuture(QtConcurrent::run(&git::Submodule::update, submodule,
                                         mCallbacks, false, true));
 }
 
@@ -2539,7 +2542,7 @@ void RepoView::updateSubmodulesAsync(const QList<SubmoduleInfo> &submodules,
                                    QString(), mWatcher, repo);
 
   entry->setBusy(true);
-  mWatcher->setFuture(QtConcurrent::run(submodule, &git::Submodule::update,
+  mWatcher->setFuture(QtConcurrent::run(&git::Submodule::update, submodule,
                                         mCallbacks, init, checkout_force));
 }
 
diff --git a/src/ui/SpellChecker.cpp b/src/ui/SpellChecker.cpp
index fb1563e13..d161cf9c4 100644
--- a/src/ui/SpellChecker.cpp
+++ b/src/ui/SpellChecker.cpp
@@ -4,7 +4,7 @@
 #include "SpellChecker.h"
 #include <QFile>
 #include <QTextStream>
-#include <QTextCodec>
+#include <QRegularExpression>
 
 SpellChecker::SpellChecker(const QString &dictionaryPath,
                            const QString &userDictionary)
@@ -26,12 +26,14 @@ SpellChecker::SpellChecker(const QString &dictionaryPath,
     QFile affixFile(affixFileName);
     if (affixFile.open(QIODevice::ReadOnly)) {
       QTextStream stream(&affixFile);
-      QRegExp enc_detector("^\\s*SET\\s+([A-Z0-9\\-]+)\\s*",
-                           Qt::CaseInsensitive);
+      QRegularExpression enc_detector(
+          "^\\s*SET\\s+([A-Z0-9\\-]+)\\s*",
+          QRegularExpression::CaseInsensitiveOption);
       QString line = stream.readLine();
       while (!line.isEmpty()) {
-        if (enc_detector.indexIn(line) >= 0) {
-          encoding = enc_detector.cap(1);
+        auto match = enc_detector.match(line);
+        if (match.hasMatch() >= 0) {
+          encoding = match.captured(1);
           break;
         }
         line = stream.readLine();
@@ -40,7 +42,9 @@ SpellChecker::SpellChecker(const QString &dictionaryPath,
       mValid = true;
     }
 
-    mCodec = QTextCodec::codecForName(encoding.toLatin1().constData());
+    auto conv =
+        QStringConverter::encodingForName(encoding.toLocal8Bit().data());
+    mEncoding = conv ? conv.value() : QStringConverter::System;
 
     // Add user dictionary words to spell checker.
     if (!mUserDictionary.isEmpty()) {
@@ -49,7 +53,8 @@ SpellChecker::SpellChecker(const QString &dictionaryPath,
         QTextStream stream(&userDictonaryFile);
         QString line = stream.readLine();
         while (!line.isEmpty()) {
-          mHunspell->add(mCodec->fromUnicode(line).constData());
+          QByteArray ba = QStringEncoder{mEncoding}.encode(line);
+          mHunspell->add(ba.toStdString());
           line = stream.readLine();
         }
         userDictonaryFile.close();
@@ -62,29 +67,33 @@ SpellChecker::~SpellChecker() { delete mHunspell; }
 
 bool SpellChecker::spell(const QString &word) {
   // Encode from Unicode to the encoding used by current dictionary.
-  return mHunspell->spell(mCodec->fromUnicode(word).toStdString());
+  QByteArray ba = QStringEncoder{mEncoding}.encode(word);
+  return mHunspell->spell(ba.toStdString());
 }
 
 QStringList SpellChecker::suggest(const QString &word) {
   QStringList suggestions;
 
   // Retrive suggestions for word.
-  std::vector<std::string> suggestion =
-      mHunspell->suggest(mCodec->fromUnicode(word).toStdString());
+  QByteArray ba = QStringEncoder{mEncoding}.encode(word);
+  std::vector<std::string> suggestion = mHunspell->suggest(ba.toStdString());
 
   // Decode from the encoding used by current dictionary to Unicode.
+  auto decoder = QStringDecoder{mEncoding};
   foreach (const std::string &str, suggestion)
-    suggestions.append(mCodec->toUnicode(str.data()));
+    suggestions.append(decoder.decode(str.data()));
 
   return suggestions;
 }
 
 void SpellChecker::ignoreWord(const QString &word) {
-  mHunspell->add(mCodec->fromUnicode(word).constData());
+  QByteArray ba = QStringEncoder{mEncoding}.encode(word);
+  mHunspell->add(ba.toStdString());
 }
 
 void SpellChecker::addToUserDict(const QString &word) {
-  mHunspell->add(mCodec->fromUnicode(word).constData());
+  QByteArray ba = QStringEncoder{mEncoding}.encode(word);
+  mHunspell->add(ba.toStdString());
 
   if (!mUserDictionary.isEmpty()) {
     QFile userDictonaryFile(mUserDictionary);
diff --git a/src/ui/SpellChecker.h b/src/ui/SpellChecker.h
index f244bee6c..4dd1d88ce 100644
--- a/src/ui/SpellChecker.h
+++ b/src/ui/SpellChecker.h
@@ -4,6 +4,7 @@
 #define SPELLCHECKER_H
 
 #include <QString>
+#include <QStringConverter>
 
 class Hunspell;
 
@@ -24,7 +25,7 @@ class SpellChecker {
 private:
   Hunspell *mHunspell = nullptr;
 
-  QTextCodec *mCodec;
+  QStringConverter::Encoding mEncoding;
   QString mUserDictionary;
 
   bool mValid = false;
diff --git a/src/ui/ToolBar.cpp b/src/ui/ToolBar.cpp
index 2be9e76fe..4ec2a2a89 100644
--- a/src/ui/ToolBar.cpp
+++ b/src/ui/ToolBar.cpp
@@ -29,6 +29,7 @@
 #include <QToolButton>
 #include <QWindow>
 #include <QtMath>
+#include <QRegularExpression>
 
 namespace {
 
@@ -944,7 +945,7 @@ ToolBar::ToolBar(MainWindow *parent) : QToolBar(parent) {
 
   // Hook up star button to search field.
   connect(mStarButton, &QToolButton::toggled, [this](bool checked) {
-    QStringList terms = mSearchField->text().split(QRegExp("\\s+"));
+    QStringList terms = mSearchField->text().split(QRegularExpression("\\s+"));
     if (checked) {
       terms.append(kStarredQuery);
     } else {
@@ -958,7 +959,7 @@ ToolBar::ToolBar(MainWindow *parent) : QToolBar(parent) {
     QSignalBlocker blocker(mStarButton);
     (void)blocker;
 
-    QStringList terms = mSearchField->text().split(QRegExp("\\s+"));
+    QStringList terms = mSearchField->text().split(QRegularExpression("\\s+"));
     mStarButton->setChecked(terms.contains(kStarredQuery));
   });
 }
diff --git a/src/ui/TreeView.cpp b/src/ui/TreeView.cpp
index 22a760be9..770847e3e 100644
--- a/src/ui/TreeView.cpp
+++ b/src/ui/TreeView.cpp
@@ -129,7 +129,8 @@ void TreeView::discard(DiffTreeModel *model, const QModelIndex &index) {
 bool TreeView::eventFilter(QObject *obj, QEvent *event) {
   if (event->type() == QEvent::MouseButtonPress) {
     QWidget *TreeViewport = static_cast<QWidget *>(obj);
-    QPoint globalPos = static_cast<QMouseEvent *>(event)->globalPos();
+    QPoint globalPos =
+        static_cast<QMouseEvent *>(event)->globalPosition().toPoint();
     QModelIndex index = indexAt(viewport()->mapFromGlobal(globalPos));
     if (!TreeViewport->hasFocus() && index.row() < 0) {
       TreeViewport->setFocus();
@@ -292,7 +293,8 @@ void TreeView::deselectAll() {
 }
 
 QRect TreeView::checkRect(const QModelIndex &index) {
-  QStyleOptionViewItem options = viewOptions();
+  QStyleOptionViewItem options;
+  initViewItemOption(&options);
   options.rect = visualRect(index);
   options.features |= QStyleOptionViewItem::HasCheckIndicator;
 
diff --git a/src/ui/ViewDelegate.cpp b/src/ui/ViewDelegate.cpp
index 8e69662ef..af130cdc2 100644
--- a/src/ui/ViewDelegate.cpp
+++ b/src/ui/ViewDelegate.cpp
@@ -31,7 +31,7 @@ void ViewDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
     // Add extra space.
     opt.rect.adjust(leftAdjust, 0, rightAdjust, 0);
 
-    for (int i = 0; i < status.count(); ++i) {
+    for (int i = 0; i < status.size(); ++i) {
       int x = opt.rect.x() + opt.rect.width();
       int y = opt.rect.y() + (opt.rect.height() / 2);
       QRect rect(mMultiColumn ? opt.rect.x() : x - width, y - (height / 2),
diff --git a/src/update/CMakeLists.txt b/src/update/CMakeLists.txt
index 530376d5b..fb980d3fc 100644
--- a/src/update/CMakeLists.txt
+++ b/src/update/CMakeLists.txt
@@ -13,14 +13,14 @@ target_link_libraries(
   conf
   ${LIBCMARK_LIBRARIES}
   git
-  Qt5::Network
-  Qt5::Widgets
+  Qt6::Network
+  Qt6::Widgets
   ${UPDATER_IMPL_LIBS})
 
 set_target_properties(update PROPERTIES AUTOMOC ON)
 
 add_executable(relauncher relauncher.cpp)
-target_link_libraries(relauncher Qt5::Core)
+target_link_libraries(relauncher Qt6::Core)
 
 set_target_properties(relauncher PROPERTIES RUNTIME_OUTPUT_DIRECTORY
                                             $<TARGET_FILE_DIR:gittyup>)
diff --git a/src/update/relauncher.cpp b/src/update/relauncher.cpp
index 0e0637c0a..ad14eab91 100644
--- a/src/update/relauncher.cpp
+++ b/src/update/relauncher.cpp
@@ -45,7 +45,7 @@ int main(int argc, char *argv[]) {
 #endif
 
   // Restart from the path argument.
-  QProcess::startDetached(args.first());
+  QProcess::startDetached(args.first(), QStringList());
 
   return 0;
 }
diff --git a/src/util/CMakeLists.txt b/src/util/CMakeLists.txt
index 4d039839f..b81930009 100644
--- a/src/util/CMakeLists.txt
+++ b/src/util/CMakeLists.txt
@@ -1,6 +1,6 @@
 add_library(util Path.cpp Debug.h Debug.cpp)
 
-target_link_libraries(util Qt5::Core)
+target_link_libraries(util Qt6::Core)
 target_include_directories(util INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})
 
 set_target_properties(util PROPERTIES AUTOMOC ON)
diff --git a/src/watcher/CMakeLists.txt b/src/watcher/CMakeLists.txt
index 16de10f5b..2818a4f10 100644
--- a/src/watcher/CMakeLists.txt
+++ b/src/watcher/CMakeLists.txt
@@ -13,6 +13,6 @@ add_library(watcher RepositoryWatcher.cpp ${WATCHER_IMPL_FILE})
 
 target_include_directories(watcher PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
 
-target_link_libraries(watcher git Qt5::Core ${WATCHER_IMPL_LIBS})
+target_link_libraries(watcher git Qt6::Core ${WATCHER_IMPL_LIBS})
 
 set_target_properties(watcher PROPERTIES AUTOMOC ON)
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 10053099d..99ba8fe34 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -23,10 +23,10 @@ macro(test)
   endif()
 
   if(WIN32)
-    find_package(Qt5Gui)
+    find_package(Qt6Gui)
     string(REPLACE ";" "\;" NEWPATH "$ENV{PATH}")
     string(REPLACE ";" "\;" PLUGIN_PATH
-                   "$<TARGET_FILE_DIR:Qt5::QOffscreenIntegrationPlugin>")
+                   "$<TARGET_FILE_DIR:Qt6::QOffscreenIntegrationPlugin>")
 
     if(${ARG_NO_WIN32_OFFSCREEN})
       set(PLATFORM "windows")
@@ -73,7 +73,7 @@ set(CMAKE_DISABLE_TESTING ON)
 add_subdirectory(dep/zip)
 
 add_library(testlib EXCLUDE_FROM_ALL Test.cpp)
-target_link_libraries(testlib app git ui Qt5::Test zip)
+target_link_libraries(testlib app git ui Qt6::Test zip)
 target_include_directories(testlib PRIVATE ${CMAKE_SOURCE_DIR}/src)
 target_compile_definitions(
   testlib
@@ -92,10 +92,10 @@ test(NAME bare_repo)
 test(NAME init_repo)
 test(NAME merge)
 test(NAME external_tools_dialog)
-test(NAME branches_panel NO_WIN32_OFFSCREEN)
-test(NAME editor NO_WIN32_OFFSCREEN)
+test(NAME branches_panel)
+test(NAME editor)
 test(NAME index)
-test(NAME line_endings NO_WIN32_OFFSCREEN)
+test(NAME line_endings)
 test(NAME log)
 test(NAME main_window)
 test(NAME new_branch_dialog)
diff --git a/test/amend.cpp b/test/amend.cpp
index 475aebee6..b85a40ed3 100644
--- a/test/amend.cpp
+++ b/test/amend.cpp
@@ -57,10 +57,12 @@ void TestAmend::testAmend() {
 
   auto authorSignature = repo.signature(
       "New Author", "New Author Email",
-      QDateTime::fromString("Sun May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
+
+  QString dateAuthor = "Mon May 23 10:36:26 2022 +0200";
   auto committerSignature = repo.signature(
       "New Committer", "New Committer Email",
-      QDateTime::fromString("Sun May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
 
   Tree tree;
   c.amend(authorSignature, committerSignature, commitMessage, tree);
@@ -73,12 +75,12 @@ void TestAmend::testAmend() {
   QCOMPARE(c.author().name(), "New Author");
   QCOMPARE(
       c.author().date(),
-      QDateTime::fromString("Sun May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
   QCOMPARE(c.committer().name(), "New Committer");
   QCOMPARE(c.committer().email(), "New Committer Email");
   QCOMPARE(
       c.committer().date(),
-      QDateTime::fromString("Sun May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
 }
 
 void TestAmend::testAmendAddFile() {
@@ -196,10 +198,10 @@ void TestAmend::testAmendDialog() {
   Test::ScratchRepository repo;
   auto authorSignature = repo->signature(
       "New Author", "New Author Email",
-      QDateTime::fromString("Sun May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
   auto committerSignature = repo->signature(
       "New Committer", "New Committer Email",
-      QDateTime::fromString("Sun May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
 
   {
     AmendDialog d(authorSignature, committerSignature, "Test commit message");
@@ -241,7 +243,7 @@ void TestAmend::testAmendDialog() {
                ContributorInfo::SelectedDateTimeType::Original);
       QCOMPARE(authorCommitDate->isVisible(), false);
       QCOMPARE(info.authorInfo.commitDate,
-               QDateTime::fromString("Sun May 23 10:36:26 2022 +0200",
+               QDateTime::fromString("Mon May 23 10:36:26 2022 +0200",
                                      Qt::RFC2822Date));
 
       // manual
@@ -290,7 +292,7 @@ void TestAmend::testAmendDialog() {
                ContributorInfo::SelectedDateTimeType::Original);
       QCOMPARE(committerCommitDate->isVisible(), false);
       QCOMPARE(info.committerInfo.commitDate,
-               QDateTime::fromString("Sun May 23 11:36:26 2022 +0200",
+               QDateTime::fromString("Mon May 23 11:36:26 2022 +0200",
                                      Qt::RFC2822Date));
 
       // manual
@@ -318,10 +320,10 @@ void TestAmend::testAmendDialog2() {
   Test::ScratchRepository repo;
   auto authorSignature = repo->signature(
       "New Author", "New Author Email",
-      QDateTime::fromString("Sun May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
   auto committerSignature = repo->signature(
       "New Committer", "New Committer Email",
-      QDateTime::fromString("Sun May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
 
   AmendDialog d(authorSignature, committerSignature, "Test commit message");
 
@@ -373,10 +375,10 @@ void TestAmend::testAmendDialogNewLineInMessage() {
   Test::ScratchRepository repo;
   auto authorSignature = repo->signature(
       "New Author", "New Author Email",
-      QDateTime::fromString("Sun May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 10:36:26 2022 +0200", Qt::RFC2822Date));
   auto committerSignature = repo->signature(
       "New Committer", "New Committer Email",
-      QDateTime::fromString("Sun May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
+      QDateTime::fromString("Mon May 23 11:36:26 2022 +0200", Qt::RFC2822Date));
 
   AmendDialog d(authorSignature, committerSignature,
                 "Test commit message\nNewLine");