diff --git a/gulpfile.mjs b/gulpfile.mjs
index f1876aed2..e694e8357 100644
--- a/gulpfile.mjs
+++ b/gulpfile.mjs
@@ -2041,6 +2041,82 @@ gulp.task(
   )
 );
 
+gulp.task("lint-licenses", function (done) {
+  console.log("\n### Checking license headers");
+
+  const jsRE =
+    /^(?:#[^\n]*\n)?\/\* Copyright \d{4} Mozilla Foundation\n \*\n \* Licensed under the Apache License, Version 2\.0 \(the "License"\);/;
+  const htmlRE = /^<!doctype html>\n<!--\nCopyright \d{4} Mozilla Foundation\n/;
+
+  // Files with non-standard license headers (different copyright holder,
+  // different license, or missing license).
+  const NON_STANDARD_HEADER_FILES = new Set([
+    "examples/learning/helloworld.html",
+    "examples/learning/helloworld64.html",
+    "examples/learning/prevnext.html",
+    "examples/node/getinfo.mjs",
+    "examples/text-only/index.html",
+    "examples/webpack/index.html",
+    "examples/webpack/main.mjs",
+    "examples/webpack/webpack.config.js",
+    "test/add_test.mjs",
+    "src/license_header_libre.js",
+    "src/shared/murmurhash3.js",
+    "test/font/font_core_spec.js",
+    "test/font/font_fpgm_spec.js",
+    "test/font/font_os2_spec.js",
+    "test/font/font_post_spec.js",
+    "test/reporter.js",
+    "test/resources/reftest-analyzer.css",
+    "test/resources/reftest-analyzer.js",
+    "test/stats/statcmp.js",
+    "web/grab_to_pan.js",
+    "web/toggle_button.css",
+  ]);
+
+  const errors = [];
+
+  gulp
+    .src(
+      [
+        "{src,web,test,examples}/**/*.{js,mjs,css}",
+        "examples/**/*.html",
+        "!web/wasm/**/*",
+      ],
+      {
+        base: ".",
+      }
+    )
+    .on("data", function (file) {
+      const relativePath = file.relative;
+      const content = file.contents.toString();
+      const re = relativePath.endsWith(".html") ? htmlRE : jsRE;
+
+      if (NON_STANDARD_HEADER_FILES.has(relativePath)) {
+        if (re.test(content)) {
+          console.warn(
+            `  ${relativePath} has a standard license header, but is in the list of non-standard header files list.`
+          );
+        }
+        return;
+      }
+      if (!re.test(content)) {
+        errors.push(relativePath);
+      }
+    })
+    .on("end", function () {
+      if (errors.length > 0) {
+        for (const file of errors.sort()) {
+          console.log(`  Invalid license header: ${file}`);
+        }
+        done(new Error("License header check failed."));
+        return;
+      }
+      console.log("files checked, no errors found");
+      done();
+    });
+});
+
 gulp.task("lint", function (done) {
   console.log("\n### Linting JS/CSS/JSON/SVG/HTML files");
 
@@ -2111,8 +2187,7 @@ gulp.task("lint", function (done) {
             return;
           }
 
-          console.log("files checked, no errors found");
-          done();
+          gulp.task("lint-licenses")(done);
         });
       });
     });
diff --git a/src/core/jpg.js b/src/core/jpg.js
index 90ef8ade9..c0985a351 100644
--- a/src/core/jpg.js
+++ b/src/core/jpg.js
@@ -1,13 +1,13 @@
 /* Copyright 2014 Mozilla Foundation
  *
- * Licensed under the Apache License, Version 2.0 (the 'License');
+ * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an 'AS IS' BASIS,
+ * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
diff --git a/test/downloadutils.mjs b/test/downloadutils.mjs
index aee1f4ae7..03506a75b 100644
--- a/test/downloadutils.mjs
+++ b/test/downloadutils.mjs
@@ -1,5 +1,4 @@
-/*
- * Copyright 2014 Mozilla Foundation
+/* Copyright 2014 Mozilla Foundation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
diff --git a/test/font/fontutils.js b/test/font/fontutils.js
index d5e1972db..17d153046 100644
--- a/test/font/fontutils.js
+++ b/test/font/fontutils.js
@@ -1,5 +1,4 @@
-/*
- * Copyright 2013 Mozilla Foundation
+/* Copyright 2013 Mozilla Foundation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
diff --git a/test/font/ttxdriver.mjs b/test/font/ttxdriver.mjs
index ba24f20ad..65213edf5 100644
--- a/test/font/ttxdriver.mjs
+++ b/test/font/ttxdriver.mjs
@@ -1,5 +1,4 @@
-/*
- * Copyright 2014 Mozilla Foundation
+/* Copyright 2014 Mozilla Foundation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
diff --git a/test/integration/thumbnail_view_spec.mjs b/test/integration/thumbnail_view_spec.mjs
index 506f636c1..4df10495a 100644
--- a/test/integration/thumbnail_view_spec.mjs
+++ b/test/integration/thumbnail_view_spec.mjs
@@ -1,3 +1,18 @@
+/* Copyright 2026 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 import {
   awaitPromise,
   closePages,
diff --git a/test/test.mjs b/test/test.mjs
index 7dd726c6c..07722fb3a 100644
--- a/test/test.mjs
+++ b/test/test.mjs
@@ -1,5 +1,4 @@
-/*
- * Copyright 2014 Mozilla Foundation
+/* Copyright 2014 Mozilla Foundation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
diff --git a/test/testutils.mjs b/test/testutils.mjs
index 5b7c6e982..70a37f471 100644
--- a/test/testutils.mjs
+++ b/test/testutils.mjs
@@ -1,5 +1,4 @@
-/*
- * Copyright 2014 Mozilla Foundation
+/* Copyright 2014 Mozilla Foundation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
diff --git a/test/webserver.mjs b/test/webserver.mjs
index ac36f1451..e8aec4e34 100644
--- a/test/webserver.mjs
+++ b/test/webserver.mjs
@@ -1,5 +1,4 @@
-/*
- * Copyright 2014 Mozilla Foundation
+/* Copyright 2014 Mozilla Foundation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
