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"CORS request not http" error when loading file:/// URI after setting privacy:file_unique_origin to false

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I've created an HTML page while trying out a JavaScript library and am loading both the page and its data source (a JSON file) from local files for now, using file:/// URIs. A week or two ago, when I first tried this, I encountered a "CORS request not http" error, as described here, when trying to load the JSON file. In my about:config, I set the privacy.file_unique_origin preference to false, after which I was able to load the JSON file successfully.

A couple of days ago, though, I started to see the "CORS request not http" error again, and I have seen it every time I have loaded the page since then, despite confirming that privacy.file_unique_origin was still set to false. I've tried several things to try to get that preference to take effect again: resetting privacy.file_unique_origin to true, setting it back to false, and restarting Firefox; reinstalling Firefox; and refreshing Firefox.

Screenshots of the error message and the privacy.file_unique_origin preference are attached. I'd appreciate any suggestions of what I should try to get the JSON file:/// resource to load successfully again. Thank you.

Attached screenshots

All Replies (1)

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Hi Sam Duncan:

This forum is focused on user support questions. It's best to ask web development questions on other forums (which i guess is unclear even though we have an article about this Where to go for developer support)

For web developer questions please:

1. ask it in stack overflow and tag it firefox

2. or you can ask on discourse if it overlaps with Firefox Developer tools:

I hope that helps!