diff --git a/.clj-kondo/config.edn b/.clj-kondo/config.edn
new file mode 100644
index 00000000..9fe3d39e
--- /dev/null
+++ b/.clj-kondo/config.edn
@@ -0,0 +1,7 @@
+{:lint-as {hiccup.def/defhtml clojure.core/defn}
+ :linters
+ {:deprecated-var
+  {:exclude
+   {ring.middleware.file-info/file-info-response
+    {:defs [ring.middleware.file-info/wrap-file-info]
+     :namespaces [ring.middleware.test.file-info]}}}}}
diff --git a/ring-core-protocols/src/ring/core/protocols.clj b/ring-core-protocols/src/ring/core/protocols.clj
index 0c30b7e4..6de7c5bb 100644
--- a/ring-core-protocols/src/ring/core/protocols.clj
+++ b/ring-core-protocols/src/ring/core/protocols.clj
@@ -37,7 +37,7 @@
     (io/writer output-stream)))
 
 (extend-protocol StreamableResponseBody
-  (Class/forName "[B")
+  #_{:clj-kondo/ignore [:syntax]} (Class/forName "[B")
   (write-body-to-stream [body _ ^OutputStream output-stream]
     (.write output-stream ^bytes body)
     (.close output-stream))
diff --git a/ring-core/src/ring/middleware/content_type.clj b/ring-core/src/ring/middleware/content_type.clj
index b093e59a..10ebaa27 100644
--- a/ring-core/src/ring/middleware/content_type.clj
+++ b/ring-core/src/ring/middleware/content_type.clj
@@ -14,7 +14,7 @@
   ([response request]
    (content-type-response response request {}))
   ([response request options]
-   (if response
+   (when response
      (if (get-header response "Content-Type")
        response
        (let [mime-type (guess-mime-type request response (:mime-types options))]
diff --git a/ring-core/src/ring/middleware/file.clj b/ring-core/src/ring/middleware/file.clj
index b46eaab3..d8db451b 100644
--- a/ring-core/src/ring/middleware/file.clj
+++ b/ring-core/src/ring/middleware/file.clj
@@ -13,7 +13,7 @@
   "Ensures that a directory exists at the given path, throwing if one does not."
   [dir-path]
   (let [dir (io/as-file dir-path)]
-    (if-not (.exists dir)
+    (when-not (.exists dir)
       (throw (Exception. (format "Directory does not exist: %s" dir-path))))))
 
 (defn file-request
@@ -27,7 +27,7 @@
                          :index-files? true
                          :allow-symlinks? false}
                         options)]
-     (if (#{:get :head} (:request-method request))
+     (when (#{:get :head} (:request-method request))
        (let [path (subs (codec/url-decode (request/path-info request)) 1)]
          (-> (response/file-response path options)
              (head/head-response request)))))))
diff --git a/ring-core/src/ring/middleware/file_info.clj b/ring-core/src/ring/middleware/file_info.clj
index 070cf664..46361e11 100644
--- a/ring-core/src/ring/middleware/file_info.clj
+++ b/ring-core/src/ring/middleware/file_info.clj
@@ -7,7 +7,7 @@
             [ring.util.mime-type :refer [ext-mime-type]]
             [ring.util.io :refer [last-modified-date]])
   (:import [java.io File]
-           [java.util Date Locale TimeZone]
+           [java.util Locale TimeZone]
            [java.text SimpleDateFormat]))
 
 (defn- guess-mime-type
@@ -17,17 +17,17 @@
   (or (ext-mime-type (.getPath file) mime-types)
       "application/octet-stream"))
 
-(defn- ^SimpleDateFormat make-http-format
+(defn- make-http-format
   "Formats or parses dates into HTTP date format (RFC 822/1123)."
-  []
+  ^SimpleDateFormat []
   ;; SimpleDateFormat is not threadsafe, so return a new instance each time
   (doto (SimpleDateFormat. "EEE, dd MMM yyyy HH:mm:ss ZZZ" Locale/US)
     (.setTimeZone (TimeZone/getTimeZone "UTC"))))
 
 (defn- not-modified-since?
   "Has the file been modified since the last request from the client?"
-  [{headers :headers :as req} last-modified]
-  (if-let [modified-since (headers "if-modified-since")]
+  [{headers :headers} last-modified]
+  (when-let [modified-since (headers "if-modified-since")]
     (not (.before (.parse (make-http-format) modified-since)
                   last-modified))))
 
diff --git a/ring-core/src/ring/middleware/flash.clj b/ring-core/src/ring/middleware/flash.clj
index ca2118dd..54d5c11c 100644
--- a/ring-core/src/ring/middleware/flash.clj
+++ b/ring-core/src/ring/middleware/flash.clj
@@ -17,7 +17,7 @@
   {:added "1.2"}
   [response request]
   (let [{:keys [session flash]} request]
-    (if response
+    (when response
       (let [session (if (contains? response :session)
                       (response :session)
                       session)
diff --git a/ring-core/src/ring/middleware/keyword_params.clj b/ring-core/src/ring/middleware/keyword_params.clj
index 6c776b70..13f25f48 100644
--- a/ring-core/src/ring/middleware/keyword_params.clj
+++ b/ring-core/src/ring/middleware/keyword_params.clj
@@ -10,7 +10,7 @@
 (defn- keyword-syntax?
   [s parse-namespaces?]
   (or (re-matches re-plain-keyword s)
-      (if parse-namespaces? (re-matches re-namespaced-keyword s))))
+      (when parse-namespaces? (re-matches re-namespaced-keyword s))))
 
 (defn- keyify-params [target parse-namespaces?]
   (cond
diff --git a/ring-core/src/ring/middleware/multipart_params/temp_file.clj b/ring-core/src/ring/middleware/multipart_params/temp_file.clj
index bb6b3791..bdc592c8 100644
--- a/ring-core/src/ring/middleware/multipart_params/temp_file.clj
+++ b/ring-core/src/ring/middleware/multipart_params/temp_file.clj
@@ -26,7 +26,7 @@
       (.delete file)
       (swap! file-set disj file))))
 
-(defn- ^File make-temp-file [file-set]
+(defn- make-temp-file ^File [file-set]
   (let [temp-file (File/createTempFile "ring-multipart-" nil)]
     (swap! file-set conj temp-file)
     temp-file))
diff --git a/ring-core/src/ring/middleware/nested_params.clj b/ring-core/src/ring/middleware/nested_params.clj
index 7b176d92..0a8776e1 100644
--- a/ring-core/src/ring/middleware/nested_params.clj
+++ b/ring-core/src/ring/middleware/nested_params.clj
@@ -12,7 +12,7 @@
     => [\"foo\" \"bar\" \"\" \"baz\"]"
   [param-name]
   (let [[_ k ks] (re-matches #"(?s)(.*?)((?:\[.*?\])*)" (name param-name))
-        keys     (if ks (map second (re-seq #"\[(.*?)\]" ks)))]
+        keys     (when ks (map second (re-seq #"\[(.*?)\]" ks)))]
     (cons k keys)))
 
 (defn- assoc-vec [m k v]
diff --git a/ring-core/src/ring/middleware/not_modified.clj b/ring-core/src/ring/middleware/not_modified.clj
index 3249d9d5..99a1d09e 100644
--- a/ring-core/src/ring/middleware/not_modified.clj
+++ b/ring-core/src/ring/middleware/not_modified.clj
@@ -2,15 +2,15 @@
   "Middleware that returns a 304 Not Modified response for responses with
   Last-Modified headers."
   (:require [ring.util.time :refer [parse-date]]
-            [ring.util.response :refer [status get-header header]]
+            [ring.util.response :refer [get-header header]]
             [ring.util.io :refer [close!]]))
 
 (defn- etag-match? [request response]
-  (if-let [etag (get-header response "ETag")]
+  (when-let [etag (get-header response "ETag")]
     (= etag (get-header request "if-none-match"))))
 
-(defn- ^java.util.Date date-header [response header]
-  (if-let [http-date (get-header response header)]
+(defn- date-header ^java.util.Date [response header]
+  (when-let [http-date (get-header response header)]
     (parse-date http-date)))
 
 (defn- not-modified-since? [request response]
diff --git a/ring-core/src/ring/middleware/resource.clj b/ring-core/src/ring/middleware/resource.clj
index fb205546..28619f24 100644
--- a/ring-core/src/ring/middleware/resource.clj
+++ b/ring-core/src/ring/middleware/resource.clj
@@ -13,7 +13,7 @@
   ([request root-path]
    (resource-request request root-path {}))
   ([request root-path options]
-   (if (#{:head :get} (:request-method request))
+   (when (#{:head :get} (:request-method request))
      (let [path (subs (codec/url-decode (request/path-info request)) 1)]
        (-> (response/resource-response path (assoc options :root root-path))
            (head/head-response request))))))
diff --git a/ring-core/src/ring/middleware/session.clj b/ring-core/src/ring/middleware/session.clj
index 12d30b0a..7bfbe636 100644
--- a/ring-core/src/ring/middleware/session.clj
+++ b/ring-core/src/ring/middleware/session.clj
@@ -19,14 +19,14 @@
    :cookie-attrs (merge {:path "/"
                          :http-only true}
                         (options :cookie-attrs)
-                        (if-let [root (options :root)]
+                        (when-let [root (options :root)]
                           {:path root}))})
 
 (defn- bare-session-request
   [request {:keys [store cookie-name]}]
   (let [req-key  (get-in request [:cookies cookie-name :value])
         session  (store/read-session store req-key)
-        session-key (if session req-key)]
+        session-key (when session req-key)]
     (merge request {:session (or session {})
                     :session/key session-key})))
 
@@ -43,7 +43,7 @@
 
 (defn- bare-session-response
   [response {session-key :session/key} {:keys [store cookie-name cookie-attrs]}]
-  (let [new-session-key (if (contains? response :session)
+  (let [new-session-key (when (contains? response :session)
                           (if-let [session (response :session)]
                             (if (:recreate (meta session))
                               (do
@@ -51,7 +51,7 @@
                                 (->> (vary-meta session dissoc :recreate)
                                      (store/write-session store nil)))
                               (store/write-session store session-key session))
-                            (if session-key
+                            (when session-key
                               (store/delete-session store session-key))))
         session-attrs (:session-cookie-attrs response)
         cookie {cookie-name
@@ -70,7 +70,7 @@
   ([response request]
    (session-response response request {}))
   ([response request options]
-   (if response
+   (when response
      (-> response
          (bare-session-response request options)
          (cond-> (:set-cookies? options true) cookies/cookies-response)))))
diff --git a/ring-core/src/ring/middleware/session/cookie.clj b/ring-core/src/ring/middleware/session/cookie.clj
index 2917acd4..7043af90 100644
--- a/ring-core/src/ring/middleware/session/cookie.clj
+++ b/ring-core/src/ring/middleware/session/cookie.clj
@@ -5,8 +5,7 @@
             [clojure.edn :as edn]
             [crypto.random :as random]
             [crypto.equality :as crypto])
-  (:import [java.security SecureRandom]
-           [javax.crypto Cipher Mac]
+  (:import [javax.crypto Cipher Mac]
            [javax.crypto.spec SecretKeySpec IvParameterSpec]))
 
 (def ^{:private true
@@ -74,7 +73,7 @@
 (defn- deserialize [x options]
   (edn/read-string (select-keys options [:readers]) x))
 
-(defn- ^String serialize [x options]
+(defn- serialize ^String [x options]
   {:post [(= x (deserialize % options))]}
   (pr-str x))
 
@@ -88,15 +87,15 @@
   "Retrieve a sealed Clojure data structure from a string"
   [key ^String string options]
   (let [[data mac] (.split string "--")]
-    (if-let [data (try (codec/base64-decode data)
+    (when-let [data (try (codec/base64-decode data)
                        (catch IllegalArgumentException _ nil))]
-      (if (crypto/eq? mac (hmac key data))
+      (when (crypto/eq? mac (hmac key data))
         (deserialize (decrypt key data) options)))))
 
 (deftype CookieStore [secret-key options]
   SessionStore
   (read-session [_ data]
-    (if data (unseal secret-key data options)))
+    (when data (unseal secret-key data options)))
   (write-session [_ _ data]
     (seal secret-key data options))
   (delete-session [_ _]
diff --git a/ring-core/src/ring/util/io.clj b/ring-core/src/ring/util/io.clj
index 0584ea08..d43e48a9 100644
--- a/ring-core/src/ring/util/io.clj
+++ b/ring-core/src/ring/util/io.clj
@@ -1,11 +1,9 @@
 (ns ring.util.io
   "Utility functions for handling I/O."
-  (:require [clojure.java.io :as io])
   (:import [java.io PipedInputStream
             PipedOutputStream
             ByteArrayInputStream
             File
-            Closeable
             IOException]))
 
 (defn piped-input-stream
diff --git a/ring-core/src/ring/util/mime_type.clj b/ring-core/src/ring/util/mime_type.clj
index acf4c2f0..52d81fce 100644
--- a/ring-core/src/ring/util/mime_type.clj
+++ b/ring-core/src/ring/util/mime_type.clj
@@ -104,7 +104,7 @@
 (defn- filename-ext
   "Returns the file extension of a filename or filepath."
   [filename]
-  (if-let [ext (second (re-find #"\.([^./\\]+)$" filename))]
+  (when-let [ext (second (re-find #"\.([^./\\]+)$" filename))]
     (str/lower-case ext)))
 
 (defn ext-mime-type
diff --git a/ring-core/src/ring/util/request.clj b/ring-core/src/ring/util/request.clj
index 8c00be5d..ff33fe4f 100644
--- a/ring-core/src/ring/util/request.clj
+++ b/ring-core/src/ring/util/request.clj
@@ -10,14 +10,14 @@
        "://"
        (get-in request [:headers "host"])
        (:uri request)
-       (if-let [query (:query-string request)]
+       (when-let [query (:query-string request)]
          (str "?" query))))
 
 (defn content-type
   "Return the content-type of the request, or nil if no content-type is set."
   {:added "1.3"}
   [request]
-  (if-let [type ^String (get (:headers request) "content-type")]
+  (when-let [type ^String (get (:headers request) "content-type")]
     (let [i (.indexOf type ";")]
       (if (neg? i) type (subs type 0 i)))))
 
@@ -25,7 +25,7 @@
   "Return the content-length of the request, or nil no content-length is set."
   {:added "1.3"}
   [request]
-  (if-let [^String length (get-in request [:headers "content-length"])]
+  (when-let [^String length (get-in request [:headers "content-length"])]
     (Long/valueOf length)))
 
 (defn character-encoding
@@ -39,7 +39,7 @@
   "True if a request contains a urlencoded form in the body."
   {:added "1.3"}
   [request]
-  (if-let [^String type (content-type request)]
+  (when-let [^String type (content-type request)]
     (.startsWith type "application/x-www-form-urlencoded")))
 
 (defmulti ^String body-string
diff --git a/ring-core/src/ring/util/response.clj b/ring-core/src/ring/util/response.clj
index 35c96e18..8686e27f 100644
--- a/ring-core/src/ring/util/response.clj
+++ b/ring-core/src/ring/util/response.clj
@@ -84,7 +84,7 @@
 
 (defn- canonical-path ^String [^File file]
   (str (.getCanonicalPath file)
-       (if (.isDirectory file) File/separatorChar)))
+       (when (.isDirectory file) File/separatorChar)))
 
 (defn- safe-path? [^String root ^String path]
   (.startsWith (canonical-path (File. root path))
@@ -99,7 +99,7 @@
 
 (defn- find-file-named [^File dir ^String filename]
   (let [path (File. dir filename)]
-    (if (.isFile path)
+    (when (.isFile path)
       path)))
 
 (defn- find-file-starting-with [^File dir ^String prefix]
@@ -117,13 +117,13 @@
 
 (defn- safely-find-file [^String path opts]
   (if-let [^String root (:root opts)]
-    (if (or (safe-path? root path)
+    (when (or (safe-path? root path)
             (and (:allow-symlinks? opts) (not (directory-transversal? path))))
       (File. root path))
     (File. path)))
 
 (defn- find-file [^String path opts]
-  (if-let [^File file (safely-find-file path opts)]
+  (when-let [^File file (safely-find-file path opts)]
     (cond
       (.isDirectory file)
       (and (:index-files? opts true) (find-index-file file))
@@ -156,7 +156,7 @@
   ([filepath]
    (file-response filepath {}))
   ([filepath options]
-   (if-let [file (find-file filepath options)]
+   (when-let [file (find-file filepath options)]
      (let [data (file-data file)]
        (-> (response (:content data))
            (content-length (:content-length data))
@@ -170,7 +170,7 @@
 ;; As a work-around, we'll backport the fix from CLJ-1177 into
 ;; url-as-file.
 
-(defn- ^File url-as-file [^java.net.URL u]
+(defn- url-as-file ^File [^java.net.URL u]
   (-> (.getFile u)
       (str/replace \/ File/separatorChar)
       (str/replace "+" (URLEncoder/encode "+" "UTF-8"))
@@ -265,8 +265,8 @@
 
 (defmethod resource-data :file
   [url]
-  (if-let [file (url-as-file url)]
-    (if-not (.isDirectory file)
+  (when-let [file (url-as-file url)]
+    (when-not (.isDirectory file)
       (file-data file))))
 
 (defn- add-ending-slash [^String path]
@@ -282,17 +282,17 @@
 
 (defn- connection-content-length [^java.net.URLConnection conn]
   (let [len (.getContentLength conn)]
-    (if (<= 0 len) len)))
+    (when (<= 0 len) len)))
 
 (defn- connection-last-modified [^java.net.URLConnection conn]
   (let [last-mod (.getLastModified conn)]
-    (if-not (zero? last-mod)
+    (when-not (zero? last-mod)
       (Date. last-mod))))
 
 (defmethod resource-data :jar
   [^java.net.URL url]
   (let [conn (.openConnection url)]
-    (if-not (jar-directory? conn)
+    (when-not (jar-directory? conn)
       {:content        (.getInputStream conn)
        :content-length (connection-content-length conn)
        :last-modified  (connection-last-modified conn)})))
@@ -301,7 +301,7 @@
   "Return a response for the supplied URL."
   {:added "1.2"}
   [^URL url]
-  (if-let [data (resource-data url)]
+  (when-let [data (resource-data url)]
     (-> (response (:content data))
         (content-length (:content-length data))
         (last-modified (:last-modified data)))))
@@ -337,9 +337,9 @@
          load      #(if-let [loader (:loader options)]
                       (io/resource % loader)
                       (io/resource %))]
-     (if-not (directory-transversal? root+path)
-       (if-let [resource (load root+path)]
+     (when-not (directory-transversal? root+path)
+       (when-let [resource (load root+path)]
          (let [response (url-response resource)]
-           (if (or (not (instance? File (:body response)))
-                   (safe-file-resource? response options))
+           (when (or (not (instance? File (:body response)))
+                     (safe-file-resource? response options))
              response)))))))
diff --git a/ring-core/src/ring/util/time.clj b/ring-core/src/ring/util/time.clj
index a346e93b..072b24a4 100644
--- a/ring-core/src/ring/util/time.clj
+++ b/ring-core/src/ring/util/time.clj
@@ -9,7 +9,7 @@
    :rfc1036 "EEEE, dd-MMM-yy HH:mm:ss zzz"
    :asctime "EEE MMM d HH:mm:ss yyyy"})
 
-(defn- ^SimpleDateFormat formatter [format]
+(defn- formatter ^SimpleDateFormat [format]
   (doto (SimpleDateFormat. ^String (http-date-formats format) Locale/US)
     (.setTimeZone (TimeZone/getTimeZone "GMT"))))
 
diff --git a/ring-devel/src/ring/handler/dump.clj b/ring-devel/src/ring/handler/dump.clj
index 9e617260..f2ef3d4c 100644
--- a/ring-devel/src/ring/handler/dump.clj
+++ b/ring-devel/src/ring/handler/dump.clj
@@ -38,7 +38,7 @@
       [:tbody
        (for [key ring-keys]
          (req-pair key req))]]
-     (if-let [user-keys (set/difference (set (keys req)) (set ring-keys))]
+     (when-let [user-keys (set/difference (set (keys req)) (set ring-keys))]
        (html
         [:br]
         [:table.request.user
@@ -54,5 +54,5 @@
    (println)
    (-> (response (template request))
        (content-type "text/html")))
-  ([request respond raise]
+  ([request respond _raise]
    (respond (handle-dump request))))
diff --git a/ring-devel/src/ring/middleware/lint.clj b/ring-devel/src/ring/middleware/lint.clj
index 3d20c90d..3ed94f2f 100644
--- a/ring-devel/src/ring/middleware/lint.clj
+++ b/ring-devel/src/ring/middleware/lint.clj
@@ -1,7 +1,6 @@
 (ns ring.middleware.lint
   "Middleware that checks Ring requests and responses for correctness."
-  (:require [clojure.set :as set]
-            [clojure.string :as str])
+  (:require [clojure.string :as str])
   (:import [java.io File InputStream]
            [java.security.cert X509Certificate]))
 
@@ -11,7 +10,7 @@
   argument and a printing of an invalid val."
   [val spec message]
   (try
-    (if-not (spec val)
+    (when-not (spec val)
       (throw (Exception. (format "Ring lint error: specified %s, but %s was not"
                                  message (pr-str val)))))
     (catch Exception e
diff --git a/ring-devel/src/ring/middleware/stacktrace.clj b/ring-devel/src/ring/middleware/stacktrace.clj
index d0ac396d..f1f5cf7d 100644
--- a/ring-devel/src/ring/middleware/stacktrace.clj
+++ b/ring-devel/src/ring/middleware/stacktrace.clj
@@ -7,8 +7,8 @@
   (:require [clojure.java.io :as io]
             [hiccup.core :refer [html h]]
             [hiccup.page :refer [html5]]
-            [clj-stacktrace.core :refer :all]
-            [clj-stacktrace.repl :refer :all]
+            [clj-stacktrace.core :as st]
+            [clj-stacktrace.repl :as repl]
             [ring.util.response :refer [content-type response status]]))
 
 (defn wrap-stacktrace-log
@@ -26,13 +26,13 @@
         (try
           (handler request)
           (catch Throwable ex
-            (pst-on *err* color? ex)
+            (repl/pst-on *err* color? ex)
             (throw ex))))
        ([request respond raise]
         (try
-          (handler request respond (fn [ex] (pst-on *err* color? ex) (raise ex)))
+          (handler request respond (fn [ex] (repl/pst-on *err* color? ex) (raise ex)))
           (catch Throwable ex
-            (pst-on *err* color? ex)
+            (repl/pst-on *err* color? ex)
             (throw ex))))))))
 
 (defn- style-resource [path]
@@ -41,14 +41,14 @@
 (defn- elem-partial [elem]
   (if (:clojure elem)
     [:tr.clojure
-     [:td.source (h (source-str elem))]
-     [:td.method (h (clojure-method-str elem))]]
+     [:td.source (h (repl/source-str elem))]
+     [:td.method (h (repl/clojure-method-str elem))]]
     [:tr.java
-     [:td.source (h (source-str elem))]
-     [:td.method (h (java-method-str elem))]]))
+     [:td.source (h (repl/source-str elem))]
+     [:td.method (h (repl/java-method-str elem))]]))
 
 (defn- html-exception [ex]
-  (let [[ex & causes] (iterate :cause (parse-exception ex))]
+  (let [[ex & causes] (iterate :cause (st/parse-exception ex))]
     (html5
      [:head
       [:title "Ring: Stacktrace"]
@@ -69,7 +69,7 @@
             [:tbody (map elem-partial (:trace-elems cause))]]]])]])))
 
 (defn- text-ex-response [e]
-  (-> (response (with-out-str (pst e)))
+  (-> (response (with-out-str (repl/pst e)))
       (status 500)
       (content-type "text/plain")))