Self hosted extension only downloads, Firefox does not ask for install


When the user clicks a link to the signed extension package Firefox should download and ask to install the addon. I was previously using the unsupported InstallTrigger and now removed method to trigger an install.

Since swapping to a plain download link Firefox is only ever downloading the XPI as a file, and never asking the user to install the extension. Is there a specific mime type or response attribute missing that would tell firefox is an addon for install?

Solved this problem - the content-type response header for the download must be application/x-xpinstall.

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