I would still recommend the docs from MDN and Google. If you're relatively familiar with web development in general - you can just peruse the APIs that are ava

I would still recommend the docs from MDN and Google. If you're relatively familiar with web development in general - you can just peruse the APIs that are available for extensions Chromium based: https://developer.chrome.com/docs/extensions/reference/ https://developer.chrome.com/docs/extensions/reference/ Or for Firefox: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web... Then hit the MDN "My first extension page" to get a mostly functional manifest file: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Your_first_WebExtension https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web... Get familiar with `about:debugging` in firefox, and `chrome://extensions` in chrome - you'll need them to load your test extensions. Finally - It's very worth it to read and understand the "core concepts" as outlined here, starting with the content_scripts: https://developer.chrome.com/docs/extensions/mv3/content_scripts/ https://developer.chrome.com/docs/extensions/mv3/content_scr...