Is web worker unavailable when cross-origin isolation is enabled

Question

Here are my two files, test.js and test.php.

test.js:

console.log("test.js is loaded")

test.php:

<?php
header('Content-Type: text/html; charset=UTF-8');
//header('Cross-Origin-Embedder-Policy: require-corp');
//header('Cross-Origin-Opener-Policy: same-origin');
?><!DOCTYPE html>
<html>
<title>test</title>
<script>
new Worker("/test.js")
</script></html>

The browser console prints "test.js is loaded" as expected. But if I comment out the two lines in test.php, nothing would be printed in the browser console, which means there's a problem that prevents the worker from being loaded if I enable the cross-origin isolation policy. So is there a correct way to use worker with the cross-origin isolation policy enabled?

BTW, I have to enable the cross-origin isolation policy because I need to use SharedArrayBuffer.

score 1 · Accepted Answer · answered Jul 07 '22 at 02:49

No, Web Workers are available, but your main worker script must be served with the same headers in its response, this is because the Worker does create a new realm, and you can't "downgrade" the embedder policy.

Specs link: https://html.spec.whatwg.org/multipage/origin.html#check-a-global-object's-embedder-policy.

Note that you could still use the usual blob: URL + importScripts() hack if you can't set this file's headers, but a properly configured server is alway better than hacks.

Is web worker unavailable when cross-origin isolation is enabled

1 Answers1