I am trying to make the web worker example from MDN to work when it is not served from a server but opened directly open from my local filesystem (via a via file:// URL)
The example works fine when served from Apache at http://localhost/1/simple-web-worker-gh-pages/index.html but it doesn't when it is read locally at file:///var/www/html/1/simple-web-worker-gh-pages/index.html
The developer console shows that messages are posted but there is no answer from the worker. (I tried both Firefox and Chromium.)
How can I make it to work ?
(There's a similar question failed to load script - Webworker (PDF.JS) , but my problem is different, as I don't see a "Failed to load script" error.)
Avoid developing using file:/// - you'll waste time debugging, as not everything is supposed to work there.
In case of Worker() in Firefox, this was supported a year ago, but was apparently disabled in Firefox 68.
See Firefox 68: local files now treated as cross-origin; is there a way to override? - if you set privacy.file_unique_origin to false in about:config, the example should work.