diff --git a/dom/chrome-webidl/PlacesEvent.webidl b/dom/chrome-webidl/PlacesEvent.webidl
index b7fd2f1f94b2..dccd343a23b9 100644
--- a/dom/chrome-webidl/PlacesEvent.webidl
+++ b/dom/chrome-webidl/PlacesEvent.webidl
@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
 enum PlacesEventType {
   "none",
 
diff --git a/dom/media/bridge/IPeerConnection.idl b/dom/media/bridge/IPeerConnection.idl
index 2986ef8b815f..37e66e98774c 100644
--- a/dom/media/bridge/IPeerConnection.idl
+++ b/dom/media/bridge/IPeerConnection.idl
@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
 #include "nsIThread.idl"
 #include "nsIDOMWindow.idl"
 #include "nsIPropertyBag2.idl"
diff --git a/dom/webidl/AddonEvent.webidl b/dom/webidl/AddonEvent.webidl
index 0f0e916e4d4a..5f607052078a 100644
--- a/dom/webidl/AddonEvent.webidl
+++ b/dom/webidl/AddonEvent.webidl
@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
 [Func="mozilla::AddonManagerWebAPI::IsAPIEnabled",
  Exposed=Window]
 interface AddonEvent : Event {
diff --git a/dom/webidl/TaskPriorityChangeEvent.webidl b/dom/webidl/TaskPriorityChangeEvent.webidl
index 1fc959ecb652..8a75657511ce 100644
--- a/dom/webidl/TaskPriorityChangeEvent.webidl
+++ b/dom/webidl/TaskPriorityChangeEvent.webidl
@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
 [Exposed=(Window, Worker), Pref="dom.enable_web_task_scheduling"]
 interface TaskPriorityChangeEvent : Event {
   constructor (DOMString type , TaskPriorityChangeEventInit priorityChangeEventInitDict);
diff --git a/dom/webidl/WebTaskScheduling.webidl b/dom/webidl/WebTaskScheduling.webidl
index 727484aa3fd0..24659f30598b 100644
--- a/dom/webidl/WebTaskScheduling.webidl
+++ b/dom/webidl/WebTaskScheduling.webidl
@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
 enum TaskPriority {
   "user-blocking",
   "user-visible",
diff --git a/dom/workers/nsIWorkerDebugger.idl b/dom/workers/nsIWorkerDebugger.idl
index 35b58e78e54f..931d01a4ac2a 100644
--- a/dom/workers/nsIWorkerDebugger.idl
+++ b/dom/workers/nsIWorkerDebugger.idl
@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
 #include "nsISupports.idl"
 
 interface mozIDOMWindow;
diff --git a/dom/workers/nsIWorkerDebuggerManager.idl b/dom/workers/nsIWorkerDebuggerManager.idl
index f7a0fb3091dc..f303a6f98628 100644
--- a/dom/workers/nsIWorkerDebuggerManager.idl
+++ b/dom/workers/nsIWorkerDebuggerManager.idl
@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
 #include "nsISupports.idl"
 
 interface nsISimpleEnumerator;
diff --git a/taskcluster/ci/source-test/mozlint.yml b/taskcluster/ci/source-test/mozlint.yml
index 0685d854e137..7fa4e46be8a9 100644
--- a/taskcluster/ci/source-test/mozlint.yml
+++ b/taskcluster/ci/source-test/mozlint.yml
@@ -187,6 +187,7 @@ license:
             - '**/*.ftl'
             - '**/*.h'
             - '**/*.html'
+            - '**/*.idl'
             - '**/*.js'
             - '**/*.jsm'
             - '**/*.jsx'
@@ -197,6 +198,7 @@ license:
             - '**/*.py'
             - '**/*.rs'
             - '**/*.svg'
+            - '**/*.webidl'
             - '**/*.xhtml'
             - '**/*.xml'
             - '**/*.xul'
diff --git a/tools/lint/license.yml b/tools/lint/license.yml
index 9079023c334d..472c7027b0f9 100644
--- a/tools/lint/license.yml
+++ b/tools/lint/license.yml
@@ -77,6 +77,7 @@ license:
         - .ftl
         - .h
         - .html
+        - .idl
         - .java
         - .js
         - .jsm
@@ -88,6 +89,7 @@ license:
         - .py
         - .rs
         - .svg
+        - .webidl
         - .xhtml
         - .xml
         - .xul
diff --git a/tools/lint/license/__init__.py b/tools/lint/license/__init__.py
index f8b313ec8517..a04fbf852458 100644
--- a/tools/lint/license/__init__.py
+++ b/tools/lint/license/__init__.py
@@ -133,6 +133,8 @@ def fix_me(log, filename):
         ".jsm",
         ".jsx",
         ".css",
+        ".idl",
+        ".webidl",
     ]:
         for i, l in enumerate(license_template):
             start = " "