solitesse

Firefox/Chrome extensions

— These extensions can also be used on Android devices with apps that support Chrome extensions, such as Kiwi Browser. I think it might work on the Nightly version of Firefox, but it’s a bit more tricky imo

AO3 First Tag Search (Chrome) - AO3 Primary Ship Search (Firefox)

Adds an option to to only show works that have your preferred ship tag as the first relationship tag. It’s great if you like ships that aren’t usually the main focus in fics. It only appears in the Search > Works section though.

AO3 Enhancements (Chrome / Firefox)

Adds a variety of features, like an estimated reading time, chapter stats, and the ability to hide works based on language/authors/tags... It’s great and easy to use!

Userscripts

— These userscripts work on web browsers, as well as on Android and iOS devices, with an userscript manager like Tampermonkey/Greasemonkey or Userscripts for Safari on iOS

Basically, an userscript is a piece of code changing a website behavior and sometimes adding new functionalities to it. There are many userscripts for ao3, but these are the two I find the most useful.

AO3: Kudosed and seen history

Keep tracks of fics you’ve kudosed/bookmarked/seen. It’s really useful if you have a really bad memory because of brain damage caused by TikTok tendency to forget which fics you’ve already read.

AO3: Fic's Style, Blacklist, Bookmarks

Pretty self-explanatory. You can change some reading settings (font, font size, margins, background color, text alignment…), create bookmarks that remember your exact position in a fic, and blacklist certain works (like the AO3 Enhancements extension, but it’s even more customizable).