2 files changed, 97 insertions, 0 deletions
diff --git a/tools/README.md b/tools/README.md
index 59860ca1b..e88f8d892 100644
--- a/tools/README.md
+++ b/tools/README.md
@@ -72,3 +72,16 @@ on top, somewhat similar to `git subtree`.
 2. Run `./tools/wgpu_sync.js`
 3. Double check changes, possibly patch
 4. Commit & send a PR with the updates
+
+## copyright_checker.js
+
+`copyright_checker.js` is used to check copyright headers in the codebase.
+
+To run the _copyright checker_:
+
+```sh
+deno run --allow-read --allow-run --unstable  ./tools/copyright_checker.js
+```
+
+Then it will check all code files in the repository and report any files that
+are not properly licensed.
diff --git a/tools/copyright_checker.js b/tools/copyright_checker.js
new file mode 100644
index 000000000..706f59dbd
--- /dev/null
+++ b/tools/copyright_checker.js
@@ -0,0 +1,84 @@
+#!/usr/bin/env -S deno run --unstable --allow-read --allow-run
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+
+import { getSources, ROOT_PATH } from "./util.js";
+
+const buffer = new Uint8Array(1024);
+const textDecoder = new TextDecoder();
+
+async function readFirstPartOfFile(filePath) {
+  const file = await Deno.open(filePath, { read: true });
+  try {
+    const byteCount = await file.read(buffer);
+    return textDecoder.decode(buffer.slice(0, byteCount ?? 0));
+  } finally {
+    file.close();
+  }
+}
+
+async function checkCopyright() {
+  const sourceFiles = await getSources(ROOT_PATH, [
+    // js and ts
+    "*.js",
+    "*.ts",
+    ":!:.github/mtime_cache/action.js",
+    ":!:cli/tests/testdata/**",
+    ":!:cli/bench/testdata/**",
+    ":!:cli/tsc/dts/**",
+    ":!:cli/tsc/*typescript.js",
+    ":!:cli/tsc/compiler.d.ts",
+    ":!:test_util/wpt/**",
+    ":!:tools/**", // these files are starts with `#!/usr/bin/env`
+    ":!:cli/tools/init/templates/**",
+
+    // rust
+    "*.rs",
+    ":!:ops/optimizer_tests/**",
+
+    // toml
+    "*Cargo.toml",
+  ]);
+
+  let totalCount = 0;
+  const sourceFilesSet = new Set(sourceFiles);
+
+  for (const file of sourceFilesSet) {
+    const ERROR_MSG = "Copyright header is missing: ";
+
+    const fileText = await readFirstPartOfFile(file);
+    if (file.endsWith("Cargo.toml")) {
+      if (
+        !fileText.startsWith(
+          "# Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.",
+        )
+      ) {
+        console.log(ERROR_MSG + file);
+        totalCount += 1;
+      }
+      continue;
+    }
+
+    if (
+      !fileText.startsWith(
+        "// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.",
+      )
+    ) {
+      console.log(ERROR_MSG + file);
+      totalCount += 1;
+    }
+  }
+
+  console.log("\nTotal errors: " + totalCount);
+
+  if (totalCount > 0) {
+    Deno.exit(1);
+  }
+}
+
+async function main() {
+  await Deno.chdir(ROOT_PATH);
+
+  await checkCopyright();
+}
+
+await main();