https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Your_first_WebExtension https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Getting_started_with_web-ext I don't think I want the node dependency. How to tell firefox to reload the extension? about:debugging How to permanently install the extension? https://stackoverflow.com/questions/47363481/install-a-personal-firefox-web-extension-permanently Two ways: - developer edition (nightly) with about:config xpinstall.signatures.required = false - let mozilla sign it as unlisted Still, xpi needs to be built: web-ext build EDIT: That builds a .zip file, so what is an .xpi file? Jesus this stuff sucks. Can I use something else? Greasemonkey? What I want to do is to run in page context anyway.