Most Popular Extensions

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HTML5 Video Everywhere!

Replace video player with Firefox native video player

Rated 4 out of 5 stars (46)
74,926 users

ReminderFox Requires Restart

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 (486)
73,750 users

Forecastfox (fix version) Requires Restart

Get international weather forecasts from AccuWeather.com and display them in any toolbar or statusbar with this highly customizable and unobtrusive extension.

Now Available for: Firefox, Thunderbird and SeaMonkey!

Rated 5 out of 5 stars (195)
68,250 users

KeeFox Requires Restart

Simple and secure password management. Login automatically, never forget another password, stay in control of your passwords and improve their security. Powered by the world-renowned KeePass Password Safe.

Rated 5 out of 5 stars (1,073)
68,232 users

Mail Merge Requires Restart Featured

Mass Mail and Personal Mail

Rated 5 out of 5 stars (143)
66,054 users

Thunderbird Conversations

This addon provides a conversation view for Thunderbird, grouping messages together and allowing you to reply "inline" thus providing a more efficient workflow.

The latest version is compatible with Thunderbird 38+ only (see below for details).

Rated 4 out of 5 stars (401)
62,876 users

Confirm-Address Requires Restart

Confirm E-mail address before sending mail

Rated 4 out of 5 stars (39)
62,674 users

Google Calendar Tab Requires Restart

Adds the Google Calendar web interface as a new tab directly into Thunderbird. Creating and viewing events works just as it would in a browser like Firefox

Rated 4 out of 5 stars (85)
62,580 users

FoxClocks

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 (311)
62,531 users

Exif Viewer Requires Restart

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

Rated 4 out of 5 stars (87)
59,426 users

Google Docs Viewer (PDF, DOCX, PPTX, XLSX, etc...) Requires Restart

View publicly-accessible PDF, DOCX, PPTX, XLSX, among other files online with Google Docs by only 2 clicks. Click as usual for your default viewer. Support bookmarked URLs. Security and your explicit viewing intention are always honored.

Rated 4 out of 5 stars (64)
57,727 users

Custom Buttons Requires Restart

Gives a possibility to create custom toolbarbuttons...

Rated 4 out of 5 stars (125)
55,700 users

Remove Duplicate Messages Requires Restart

If you have duplicate messages (e.g. from merging folders or downloading messages several times) you can use this tool to find and remove them from the selected folder and its subfolder by rightclicking on a folder and choosing "Remove duplicates..."

Rated 4 out of 5 stars (140)
54,282 users

ProfileSwitcher Requires Restart

It adds some options to launch easily other profiles and the Profile Manager.

Rated 4 out of 5 stars (97)
51,801 users

Ad-Blocker

Ad Blocker lets you block all ads, tracking & malware from the web world. It is an effective solution to browse the web without offensive and annoying ads you hate to see.

Rated 4 out of 5 stars (76)
49,053 users

rikaichan Requires Restart

Japanese to English/German/French/Russian dictionary. Just hover the mouse on top of a word, and a popup appears. Automatically de-inflects verbs and adjectives. Detailed kanji view...

Rated 5 out of 5 stars (109)
44,473 users

Copy Plain Text 2 Requires Restart

Copies text without formatting

Rated 5 out of 5 stars (81)
43,527 users

Mail Redirect Requires Restart Featured

Allow to redirect (a.k.a. "remail") mail messages to other recipients.

Rated 4 out of 5 stars (131)
43,013 users

Stationery Requires Restart

Extension to mimic Outlook Express Stationery.
Allow you to use HTML files as templates for mail. Also allow custom template in replies or forwarded mail!

Rated 4 out of 5 stars (113)
42,743 users

Addressbooks Synchronizer Requires Restart

Synchronizes selected addressbooks with other instances of thunderbird
using ftp/webdav/imap servers

Rated 4 out of 5 stars (58)
42,207 users