Extensions

uBlock Origin

Best adblock extension on the market. Use this one, not any other. You can consider Ad Nauseam instead, but I recommend this one.
Link: https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/

ClearURLs

This extension removes tracking elements from URLs.
Link: https://addons.mozilla.org/en-US/firefox/addon/clearurls/

Decentraleyes

This blocks website from requesting well-know websites (Google Hosted Libraries) for JS libraries and instead serves them locally. This addon complements adblockers like uBlock Origin.
Link: https://addons.mozilla.org/en-US/firefox/addon/decentraleyes/

Privacy Badger

Block and learns to block hidden trackers.
Link: https://addons.mozilla.org/en-US/firefox/addon/privacy-badger17/

Automagically denies cookies on most websites.
Link: https://addons.mozilla.org/en-US/firefox/addon/consent-o-matic/

CanvasBlocker

If not using LibreWolf or having enabled WebGL in LibreWolf, I recommend installing it. It prevents website from accessing a few things, like WebGL.
Link: https://addons.mozilla.org/en-US/firefox/addon/canvasblocker/

Don't Track Me Google

Removes Google's link conversion to see on which websites you clicked.
Link: https://addons.mozilla.org/en-US/firefox/addon/dont-track-me-google1/

SponsorBlock

Automagically skip sponsors (and more with some config) on YouTube videos.
Link: https://addons.mozilla.org/en-US/firefox/addon/sponsorblock/

Unhook

Remove all kinds of things from YouTube like shorts, comments, suggestions, etc.
Link: https://addons.mozilla.org/en-US/firefox/addon/youtube-recommended-videos/

YouTube No Translation

Disable auto-translation of titles, audio, descriptions, etc.
Link: https://addons.mozilla.org/en-US/firefox/addon/youtube-no-translation/

FastStream Video Player

Replaces your video player on streaming websites with a good one.
Link: https://addons.mozilla.org/en-US/firefox/addon/faststream/