diff --git a/generic-sensor/idlharness.https.window.js b/generic-sensor/idlharness.https.window.js
index f591d755209e38..db932f35c0d519 100644
--- a/generic-sensor/idlharness.https.window.js
+++ b/generic-sensor/idlharness.https.window.js
@@ -11,7 +11,7 @@ function cast(i, t) {
 
 idl_test(
   ['generic-sensor'],
-  ['dom', 'html', 'WebIDL'],
+  ['dom', 'html', 'webidl'],
   idl_array => {
     idl_array.add_objects({
       Sensor: ['cast(new Accelerometer(), Sensor)'],
diff --git a/interfaces/WebIDL.idl b/interfaces/webidl.idl
similarity index 100%
rename from interfaces/WebIDL.idl
rename to interfaces/webidl.idl
diff --git a/mediacapture-record/idlharness.window.js b/mediacapture-record/idlharness.window.js
index 2e304b0a0e6ece..99e884530c0f42 100644
--- a/mediacapture-record/idlharness.window.js
+++ b/mediacapture-record/idlharness.window.js
@@ -7,7 +7,7 @@
 
 idl_test(
   ['mediastream-recording'],
-  ['mediacapture-streams', 'FileAPI', 'html', 'dom', 'WebIDL'],
+  ['mediacapture-streams', 'FileAPI', 'html', 'dom', 'webidl'],
   idl_array => {
     // Ignored errors will be surfaced in idlharness.js's test_object below.
     let recorder, blob, error;
diff --git a/mediacapture-streams/idlharness.https.window.js b/mediacapture-streams/idlharness.https.window.js
index 41d4e1db8b639d..e8e3cdab218029 100644
--- a/mediacapture-streams/idlharness.https.window.js
+++ b/mediacapture-streams/idlharness.https.window.js
@@ -8,7 +8,7 @@
 
 idl_test(
   ['mediacapture-streams'],
-  ['WebIDL', 'dom', 'html'],
+  ['webidl', 'dom', 'html'],
   async idl_array => {
     const inputDevices = [];
     const outputDevices = [];
diff --git a/web-nfc/idlharness.https.window.js b/web-nfc/idlharness.https.window.js
index e2000abce8da4e..72b5793f48e08c 100644
--- a/web-nfc/idlharness.https.window.js
+++ b/web-nfc/idlharness.https.window.js
@@ -18,7 +18,7 @@ const message = {
 
 idl_test(
   ['web-nfc'],
-  ['html', 'dom', 'WebIDL'],
+  ['html', 'dom', 'webidl'],
   idl_array => {
     idl_array.add_objects({
       NDEFReader: ['new NDEFReader();'],
diff --git a/webidl/idlharness.any.js b/webidl/idlharness.any.js
index efc475a9879dbc..3c662ba8e63f2f 100644
--- a/webidl/idlharness.any.js
+++ b/webidl/idlharness.any.js
@@ -4,7 +4,7 @@
 "use strict";
 
 idl_test(
-  ['WebIDL'],
+  ['webidl'],
   [],
   idl_array => {
     idl_array.add_objects({
diff --git a/webrtc-identity/idlharness.https.window.js b/webrtc-identity/idlharness.https.window.js
index 8c7bf665ef6948..8eb60c960aa00b 100644
--- a/webrtc-identity/idlharness.https.window.js
+++ b/webrtc-identity/idlharness.https.window.js
@@ -5,7 +5,7 @@
 
 idl_test(
   ['webrtc-identity'],
-  ['webrtc', 'mediacapture-streams', 'html', 'dom', 'WebIDL'],
+  ['webrtc', 'mediacapture-streams', 'html', 'dom', 'webidl'],
   async idlArray => {
     idlArray.add_objects({
       RTCPeerConnection: [`new RTCPeerConnection()`],
diff --git a/webrtc/idlharness.https.window.js b/webrtc/idlharness.https.window.js
index ae18cc6353831a..ffe57ab93da817 100644
--- a/webrtc/idlharness.https.window.js
+++ b/webrtc/idlharness.https.window.js
@@ -103,7 +103,7 @@ function asyncInit() {
 
 idl_test(
   ['webrtc'],
-  ['WebIDL', 'mediacapture-streams', 'dom', 'html'],
+  ['webidl', 'mediacapture-streams', 'dom', 'html'],
   async idlArray => {
     idlArray.add_objects({
       RTCPeerConnection: [`new RTCPeerConnection()`],
diff --git a/webtransport/idlharness.https.any.js b/webtransport/idlharness.https.any.js
index ae4767c71a46bb..248bc41abe5565 100644
--- a/webtransport/idlharness.https.any.js
+++ b/webtransport/idlharness.https.any.js
@@ -6,7 +6,7 @@
 
 idl_test(
   ['webtransport'],
-  ['WebIDL', 'streams'],
+  ['webidl', 'streams'],
   idl_array => {
     idl_array.add_objects({
       WebTransport: ['webTransport'],