🦿 Lucian Marin
On Firefox I have these: app.telemetry page speed monitor, multi-account containers, h264fy, max tabs, order tabs by domain. I use macOS Light theme which I created: addons.mozilla.org....
💻 Kenneth Jensen
uBlock Origin and uMatrix, chromium. The WWW is much more pleasant. "Inspect element" is also underrated for fixing fonts or deleting pop-ups and notifications and e-stalking social media without an account (cough Instagram).
🔻 Trinity
I have a number installed in Firefox, which is probably a bad habit: Wayback Machine, User Agent Switcher, Tampermonkey, ClearURLs, Hoxx VPN, WebRTC Leak Shield, uBlock Origin, Dark Reader, SponsorBlock, Lastpass, unPaywall, Downloader for Tiktok, MEGA, SingleFile, and Download Picture from Instagram. I do use all of them though. I have more but they're so numerous I couldn't go through them all in one comment.