Font Inspector (WebExtension) – Get this Extension for 🦊 Firefox (en-US)

Download Font Inspector (WebExtension) for Firefox. Click on any element to get the font info in a page popup

Identify fonts in Chrome, Edge and Firefox using Developer Tools

Advanced Search – Get this Extension for 🦊 Firefox (en-US)

DownThemAll! – Get this Extension for 🦊 Firefox (en-US)

Treetop – Get this Extension for 🦊 Firefox (en-US)

Chromaticity – Get this Extension for 🦊 Firefox (en-US)

RESTer – Get this Extension for 🦊 Firefox (en-US)

10 Tips about WebExtension. In this article, we forego detailed…, by Allen Fang, ShopBack Tech Blog

Firefox: Legacy add-on, or WebExtension? How to find out - gHacks Tech News

JavaScript Toggle On and Off (WebExtension) – Get this Extension for 🦊 Firefox (en-US)

Laboratory (Content Security Policy / CSP Toolkit) – Get this Extension for 🦊 Firefox (en-US)

Weh Inspector – Get this Extension for 🦊 Firefox (en-US)

ContextSearch web-ext – Get this Extension for 🦊 Firefox (en-US)

Tree Style Tab For Chrome

webextension-polyfill/README.md at master · mozilla/webextension-polyfill · GitHub