I am working on a page that will be server by a small embedded webserver that I have no control of. On the page, some data transfer (XHR) should be done inside a web worker. The server will not send any cross-origin relevant headers nor will it answer preflight OPTIONS requests reasonably.

When I put the worker javascript code into a separate file, the XHR in the worker do what they should.

But I would like to avoid the need to put two files up to the server. When I put the javascript source of the worker inside the same page and use data:text/javascript;base64,' + btoa(scripttext) for the worker, then the browser will try preflight calls to the server which fails.

What option do I have to have the worker in the same page and still be able to use XHR inside the worker successfully? I.e. how can I get the browser to treat it same-origin? I mean, it is in the same file…

Thanks!