| Echofon | | - | | |
| Easy YouTube Theme Maker | | - | | |
| Easy JsBin | | - | | |
| East Asian Translator | | - | | |
| DuckDuckGo-bangs | | - | | |
| DuckDuckGo Plus | | - | | |
| DuckDuckComplete! | | - | | |
| DuckDuckBang | | - | | |
| Dualsub | | - | | |
| Dribbble New Tab | | - | | |
| Dr.Web scan link | | - | | |
| Dr.Web anti-virus link checker | | - | | |
| Download YouTube Videos in HD and MP4 | | - | | |
| Domain Whois for FirefoxTM | | - | | |
| Domain Details | | - | | |
| Docs Online Viewer | | - | | |
| Disconnect Search | | - | | |
| Diigo Toolbar for Firefox | | - | | |
| DictionarySearch | | - | | |
| Dictionary Tooltip | | - | | |
| Deng Google Bookmarks | | - | | |
| Delicious Bookmarks | | - | | |
| Define Word | | - | | |
| Datum Find Image Copies | | - | | |
| Dark YouTube Theme | | - | | |
| Danbooru Downloader | | - | | |
| Daily Dilbert | | - | | |
| DA Ghost | | - | | |
| Currency Converter | | - | | |
| Craigslist Peek | | - | | |
| Craigslist Fusion | | - | | |
| Copyright Infringement Finder | | - | | |
| Copy goo.gl URL | | - | | |
| Copy Tiny URL | | - | | |
| Copy ShortURL | | - | | |
| Copy Real Url | | - | | |
| CoolPreviews | | - | | |
| CookieRank | | - | | |
| Contextual Google Image Search | | - | | |
| Comeback Cached Link | | - | | |
| Color Change for Facebook | | - | | |
| CodeNav | | - | | |
| CloudMagic | | - | | |
| Cloud Clipboard | | - | | |
| Cleeki Firefox Express | | - | | |
| Clearly | | - | | |
| CleanTube | | - | | |
| Classic Retweet | | - | | |
| Chicky's Booru-style Image Downloader | | - | | |
| Character Identifier | | - | | |