In my JS web-application, I'm trying to store the tiles in my localstorage using web workers.
I'm using the code from this Esri sample. I just deleted line 20 in the ioWorker.js file:

 url = "/arcgisserver/apis/javascript/proxy/proxy.ashx?" + url;

But when the web worker requests a tile, I get those three errors: Error
On my side, CORS should be working fine. Is this a problem on Esri's side or have i got something wrong?

edit: Or is it not possible only with CORS, do I need a proxy-page?

  • 1
    From the sample: In order to run this sample application on your machine you'll need to update the line that sets the proxy in the ioWorker.js file to point to your proxy.. You need a local proxy.
    – Ragnar123
    Oct 17, 2013 at 20:50

1 Answer 1


Yes, you need a proxy page if the the request is not from the same domain. The proxy also needs to be under the same domain, otherwise, you'll still get this CORS error.

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