An easy-to-use font inspector to get CSS styles of the selected element
A reference for the codes to generate Emojis on popular sites like GitHub or Basecamp and Unicode characters for Twitter and Facebook. Search Emojis by name or view recently selected items. Emojis are automatically copied to the clipboard.
Quickly and easily switch between popular user-agent strings.
a customizable extension to save the images from the current tab page
'Classic Toolbar Buttons' add-on restores old toolbar button ui (known from Fx 4-7s small view, Fx 4-12s large view & Tb 5-14) for current Firefox, Thunderbird and Seamonkey versions. Beta builds on versions page!
View source code of Firefox add-ons and Chrome extensions (crx/nex/xpi) from addons.mozilla.org, the Chrome Webstore and elsewhere.
Add-on to display GitHub code in tree format
Cookie-Editor lets you efficiently create, edit and delete a cookie for the current tab. Perfect for developing, quickly testing or even manually managing your cookies for your privacy. Also supports Firefox for Android.
RusVPN - Free VPN Service
Enables the resolving of Dot-BIT domains by Namecoin. Also .emc, .coin, .lib and .bazar domains by EmerCoin. Redirecting of NXT aliases.