Firefox add-ons with "Open Source" tag

Finally, an efficient wide-spectrum content blocker. Easy on CPU and memory.

Unmatched adblock extension against advertising and pop-ups. Blocks ads on Facebook, Youtube and all other websites.

English United States (en-US) Dictionary based on GitHub: marcoagpinto/aoo-mozilla-en-dict.

A fork of Mark Tyndall's add-on, based on David Bartlett's British Dictionary R1.19 for Firefox, Thunderbird and SeaMonkey.

Userscript support for browsers, open source.

Redesign your favorite websites with Stylus, an actively developed and community driven userstyles manager. Easily install custom themes from popular online repositories, or create, edit, and manage your own personalized CSS stylesheets.

Firefox Language Pack for Afrikaans (af)

Changes the color of Firefox theme to match the website’s appearance.

Putting Flash back on the web. Designed to be easy to use, this extension will seamlessly enable you to play flash content, with no extra configuration required!

Beyond dark mode for Google Docs

Clear Firefox cache and selected browsing data from the toolbar, context menu, or F9 shortcut. Choose what to clear, pick a time range, and optionally reload the active tab.

Get free text of research papers as you browse, using Unpaywall's index of ten million legal, open-access articles.

View archived and cached versions of web pages on various search engines, such as the Wayback Machine and Archive․is.

Block the trackers that feed AI-powered attacks. Disconnect stops thousands of hidden trackers across advertising, analytics, social, and fingerprinting, making pages load up to 44% faster. Trusted to help protect 350M+ users.

Ensure Reddit always loads the old design

Set a default speed for video and audio.

Open-source music recognition extension using Shazam API (also supports Audd, ACRCloud, Tencent, and NetEase APIs as alternative backends)

Keeps YouTube content in its original language (Titles, Audio Tracks, Descriptions...)

Powerful and versatile pop-up dictionary for language learning used by 100,000+ language learners.

Integrates the D&D Beyond Character Sheet into Roll20 and Foundry VTT.

TTV LOL PRO removes most livestream ads from Twitch.

Remove ALL distracting search results, redirect shorts back to legacy page and try little visual changes suited for low resolution screens.

A strict British-English spell checker dictionary for Firefox, Thunderbird and SeaMonkey. This dictionary only includes words conforming to the preferred standard of British-English spelling.

Scrobble music all around the web!

Re-implements the google image, "View Image" button.