My list of extensions- Imagus - displays bigger image when hovered over (Imagus Mod recommended); - Sponsor Block - Skips promotions on YT videos; - TOS;DR - summarizes TOS and Privacy Policies; - Cookie Autodelete - erases cookies when you close a tab, can make you log out regularly if you don’t put an website on a whitelist, though. - Dark Reader - changes the page CSS and creates a dark mode version of any page, while it isn’t always 100% perfect, it has many useful configurations, like whitelisting websites OR words on them, changing to a light mode, but less bright version of it, setting up the time that it activates, and a few more. - Open tabs next to current/Always Right - What the names says, 2 different extensions, but on Chrome I prefer to combine them. - Wayback Machine - has an option to auto archive, can bring you to oldest or newest versions of websites and links. - Search Image - gives you 6 or so options to search for an image online, kind of combines with Imagus. - uBlock Origin - the best ad blocker so far, browsers with built in adblock use it. - Privacy Badger - blocks hidden trackers once it sees then on 3 different websites - WhatFont - displays the font name in a popup, this is more a personal thing, but I enjoy it. - Anti fingerprinting extensions can possibly help. This is a long list, but these are one of the extensions that I have and I most value, there are some otherb too, but those are more aesthetic than anything.
Foxy Gestures. I love having mouse gestures for Close Tabs on Right, Back, and Close Tab, amongst other.
Zoom Page WE, automatically zoom to full width. Really useful for “convergence” pages, ie: lazy web developers that think every browser wants a 4 word wide column. You have to set “Automatically Zoom” in preferences, it doesn’t work out of the box.
On my iPhone I have one called Save All Images. Basically you know how lots of sites especially any kind of social media where they want you there to see things… anyway they use a script or whatnot to prevent holding down on an image to get the save photo prompt. This is an extension that loads all images that are single level referenced and you can save any/all. I use it almost daily. Instagram, and the like, especially, they hate the notion of someone saving something.
In Firefox on my computer I have Element Blocker. Some websites just waste a lot of screen space so if you’re browsing a ton of content you’d like to get the most room, but some stuff takes up portions of the screen fixed and not movable. This extension lets you select an element and it makes it just disappear. It is absolutely essential.