Firefox add-ons are extensions, themes, dictionaries and language packs that change what Mozilla Firefox can do. The official source is the Mozilla Add-ons store at addons.mozilla.org (AMO). Open the Add-ons Manager from the Firefox menu under Extensions and Themes, or press Ctrl + Shift + A (Command + Shift + A on a Mac), then click Add to Firefox on any listing. Extensions with Mozilla's Recommended badge are the safest starting point.

This page explains where to find Firefox extensions, how to install them on desktop and Android, how to judge whether an add-on is safe, and which Mozilla extensions are worth installing first, grouped by task.

Where to get Firefox add-ons: the Mozilla Add-ons store

The Mozilla Add-ons store, addons.mozilla.org, is the official catalogue for Firefox add-ons, and it is the place to download them. Every listing shows the developer, user count, rating, permissions and version history. Firefox for Android has its own section of the store at addons.mozilla.org/android.

Mozilla groups add-ons into these types:

• Extensions add or change features, for example content blocking, password management or video controls.
• Themes change the look of the toolbar, tab strip, address bar and menus.
• Dictionaries add spell checking for languages that Firefox does not include by default.
• Language packs change the language of the Firefox interface.
• Search engines add more search providers to the address bar.

Plugins are a separate category. Firefox installs the few that remain automatically (Google Widevine CDM for DRM video and OpenH264 for video calls), so there is nothing to download. Older terms such as "Firefox plugins" or "Mozilla extensions" in search results usually mean the same thing as add-ons today.

How to install Firefox extensions on desktop

Installing a Firefox extension takes a few clicks from the Add-ons Manager or directly from a store listing. Mozilla's install guide describes these steps:

1. Click the Firefox menu button and select Extensions and Themes, or press Ctrl + Shift + A. The Add-ons Manager opens in a new tab.
2. Select Recommendations to browse suggestions, or click Find more add-ons to open addons.mozilla.org and search.
3. Open a listing and click + Add to Firefox (for themes the button reads + Install Theme).
4. Read the permission prompt and confirm with Add.
5. Pin the extension to the toolbar from the extensions button if you want quick access to it.

Advanced users can install a downloaded .xpi file: open the Extensions panel, click the gear icon and choose Install Add-on from file. Only do this with files from a developer you trust, because they skip the store listing where you can check reviews and history.

How to install add-ons in Firefox for Android

Firefox for Android supports extensions from its own menu, and the process mirrors desktop. Per Mozilla's Android guide:

1. Tap the three-dot menu button.
2. Tap Extensions (called Add-ons in versions before 126).
3. Tap an extension to see its details, then tap the + button.
4. Review the access it asks for and tap Add.
5. Optionally check Allow in private browsing, then tap Okay, Got it.

Each installed extension then has an Enabled slider, Settings, Details, Permissions and Remove options. Not every desktop extension has an Android build, so look for the "Available on Firefox for Android" label on the listing. Userscript managers such as Violentmonkey are available on Android too, so site tweaks you use on desktop can follow you to a phone.

Are Firefox add-ons safe? Badges and permission checks

Firefox add-ons with a Recommended or By Firefox badge have passed Mozilla review and are the safest picks, while other listings deserve a quick check before you install. Mozilla's badge documentation defines three labels:

• Recommended: chosen by Mozilla for security, functionality and user experience, manually reviewed for policy compliance, and monitored with automated checks and periodic technical reviews. Developers cannot pay to join.
• By Firefox: built by Mozilla, such as Multi-Account Containers.
• Caution: shown on add-ons Mozilla staff do not regularly review. It does not mean the add-on is unsafe, only that you should check it yourself.

For an extension without a badge, run through this checklist:

• Does the developer have a website, source code or a track record?
• Do the requested permissions match the job? A dark mode tool needs page access; a calculator does not.
• Was the add-on updated recently, and do recent reviews mention ads, redirects or new owners?
• Is there a Recommended alternative that does the same thing?

Best Firefox addons by category

The best Firefox addons solve one problem well, are actively maintained and, ideally, carry Mozilla's Recommended badge. The table below lists extensions whose store listings we checked for badge, developer activity and Android availability.

Privacy and security

uBlock Origin by Raymond Hill blocks ads, trackers and malware domains and has more than 11 million users on AMO. Pair it with Privacy Badger from the Electronic Frontier Foundation if you want behavior-based tracker blocking, and with ClearURLs to clean tracking parameters from links (our ClearURLs review explains its rules). Bitwarden covers passwords and passkeys across browsers and devices.

Firefox Multi-Account Containers is Mozilla's own extension for keeping work, shopping and social accounts apart in one window, and it can sync containers across devices.

NoScript by Giorgio Maone blocks scripts by default and lets you allow trusted sites one by one; our NoScript tips cover its lesser-known options. FoxyProxy Standard switches between proxies based on the address you visit, which helps if you use a work proxy or a VPN proxy for some sites only.

Appearance and YouTube

Dark Reader generates dark themes for sites that do not offer one; see our Dark Reader review for its filter modes. SponsorBlock uses crowdsourced timestamps to skip sponsor reads and other segments on YouTube.

Productivity and tabs

SingleFile archives a page with images and styling in one HTML file. Auto Tab Discard keeps memory use down for heavy tab users, and Violentmonkey runs userscripts that tweak individual sites.

Why Firefox still runs full-strength content blockers

Firefox still supports the extension features that full content blockers rely on, which is a practical reason to choose it over Chrome for privacy add-ons. In its Manifest V3 update, Mozilla wrote that Firefox "has no plans to deprecate MV2 and will continue to support MV2 extensions for the foreseeable future", and that it keeps the blocking webRequest API in Manifest V3 as well.

That API lets an extension inspect and cancel network requests before they load. Chromium browsers took a different path and moved users to reduced blockers such as uBlock Origin Lite (see how Edge switched uBlock Origin to the Lite edition). On Firefox, the full uBlock Origin keeps working on desktop and Android.

Mozilla also said it would give developers at least 12 months of notice if that position changes, so a sudden loss of these features is unlikely.

How to disable, remove or troubleshoot Firefox add-ons

You manage installed Firefox add-ons from the Extensions panel of the Add-ons Manager, where each one can be switched off or removed. Mozilla's removal guide lists the steps:

1. Open the menu, select Extensions and Themes, then Extensions.
2. Use the toggle next to an extension to disable it while keeping it installed.
3. To uninstall, click the three-dot icon next to the extension and choose Remove.

If pages break, Firefox slows down or settings change on their own, restart Firefox in Troubleshoot Mode, which runs the browser with add-ons disabled. If the problem disappears, re-enable extensions one at a time until it returns, then remove the one responsible. Mozilla's add-on troubleshooting article covers the process, and the about:support page holds the details to share when you ask for help.

FAQ

Related: best Chrome extensions, Firefox tab groups