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

Navigate to the folder where your extension is located. You can build it in the usual way using web-ext:

web-ext build

You can install this ZIP file permanently in Firefox by going to about:addons and dragging this file into the tab.

In order for this to work, you need to set xpinstall.signatures.required to false in about:config (works only for Nightly and maybe Developer Edition).