Most Popular Extensions

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Quick Locale Switcher

Allows you to quickly switch to a different language (User Interface, Spell Checker Dictionary and Website content) in your Mozilla application.

Rated 3 out of 5 stars (82)
154,245 users

Enigmail Featured

OpenPGP message encryption and authentication for Thunderbird and SeaMonkey.

Rated 4 out of 5 stars (181)
145,499 users

CompactHeader Featured

Add symbol in header plane to switch between compact and expanded view. Options to switch between one or two lines compact view, which buttons should be displayed in header pane. For Thunderbird 36 and older use version 2.0.9 (see version history)

Rated 5 out of 5 stars (168)
140,095 users

Bluhell Firewall No Restart

Get a faster browsing experience by blocking nasty web resources using Bluhell Firewall, the lightweight Ad-Blocker and Tracking/Privacy Protector.

Rated 5 out of 5 stars (233)
136,273 users

DOM Inspector

DOM Inspector is a tool that can be used to inspect and edit the live DOM of any web document or XUL application. The DOM can be navigated using a two-paned window displaying a variety of different views on the document and all nodes within.

Rated 5 out of 5 stars (65)
132,133 users

JavaScript Debugger

As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.

Venkman is the code name for Mozilla's JavaScript Debugger. Venkman aimed to provide a powerful JavaScript debugging environment for Mozilla based browsers.

Rated 4 out of 5 stars (50)
130,651 users

Toolbar Buttons No Restart

Adds toolbar buttons to the customize toolbar window in several programs including Firefox, Thunderbird and SeaMonkey. Some of the buttons make commonly preformed actions quicker, others add new functionality.

Rated 4 out of 5 stars (316)
126,908 users

X-notifier (for Gmail,Hotmail,Yahoo,AOL ...)

Notifier for gmail, yahoo, hotmail, aol and more webmails.
X-notifier(aka WebMail Notifier) checks your webmail accounts and notifies the number of unread emails...
Supports : gmail, yahoo, hotmail, POP3/IMAP, facebook, twitter and more

Rated 4 out of 5 stars (1,625)
102,992 users

Manually sort folders

This extension allows you to manually sort (order) your folders in the folder pane of Thunderbird or automatically sort them, but in a better way. This extension also allows you to re-order accounts in the folder pane.

Rated 4 out of 5 stars (104)
95,114 users

ReminderFox

ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.

Rated 4 out of 5 stars (492)
92,432 users

Saved Password Editor

Adds the ability to create and edit entries in the password manager.

Rated 5 out of 5 stars (205)
89,449 users

Theme Font & Size Changer No Restart

Theme Font & Size Changer lets you change the global font size and font family used for the user interface in Firefox. Design your browser with your favorite font.

Rated 5 out of 5 stars (146)
88,903 users

Signature Switch Featured

Switch the signature on/off or choose a new one from your predefined set...

Rated 4 out of 5 stars (165)
83,563 users

UnMHT No Restart

UnMHT allows you to view MHT (MHTML) web archive format files, and save complete web pages, including text and graphics, into a single MHT file in Firefox/SeaMonkey.

Rated 5 out of 5 stars (217)
78,680 users

Quicktext

Quicktext is an extension for Thunderbird that lets you create templates that can be easily inserted into your own emails.

Rated 4 out of 5 stars (274)
74,903 users

Custom Buttons

Gives a possibility to create custom toolbarbuttons...

Rated 4 out of 5 stars (86)
73,960 users

AutoProxy

Are you concerned about your privacy? Or, are you blocked from some websites by a firewall? And, are you arming yourself with a proxy? In that case, AutoProxy is designed for you! A tool to help you use your proxy automatically & efficiently.

Rated 4 out of 5 stars (414)
71,002 users

ShowIP

Show the IP address of the current page in the status bar. It also allows querying custom information services by IP (right click) and see location and avaiable vouchers for shopping sites. Additionally you can copy the IP address to the clipboard.

Rated 3 out of 5 stars (284)
67,573 users

FoxClocks No Restart

FoxClocks shows times around the world - or just your local time - at the bottom of your browser. It deals with daylight saving time so you don't have to.

Rated 4 out of 5 stars (306)
66,774 users

Exif Viewer

Displays the Exif and IPTC data in local and remote JPEG images.

Rated 4 out of 5 stars (83)
66,740 users