Install a personal firefox web extension permanently

Question

Previously, I could write an addon for personal usage packed as something.xpi and I clicked on it to install it.

After a while, mozilla introduced xpi

Answer 1

You need a "blueish" Firefox -- Developer Edition (effectively beta) or Nightly (unstable, updated every night).

You can get them from https://mozilla.org/firefox/channel/desktop/.

Then xpinstall.signatures.required will work again.

(As for permissions--you can create a GUI in a tab or a popup, but I don't think you can do it in a separate window (unless you do a webpage-style popup window). You won't be able to write to arbitrary files anywhere on the system--which is a good thing! You can write to the Downloads folder, and read/write some sort of internal storage, but that may not expose the actual files involved. For more information see https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Working_with_files.)