| KOSHIAN delフォームをポップアップで開く | | - | | |
| KOSHIAN quote futaba | | - | | |
| KOSHIAN reload futaba | | - | | |
| KOSHIAN 返信フォーム拡張 | | - | | |
| KOSHIAN 連投抑制 | | - | | |
| Keeper Password Manager ＆ Digital Vault | | - | | |
| KeyAffinity | | - | | |
| Klout | | - | | |
| Kloutify | | - | | |
| LastPass | | - | | |
| Latest BBC News | | - | | |
| Lens | | - | | |
| Let's Search | | - | | |
| Libron(リブロン) | | - | | |
| Light Dict | | - | | |
| Lighter | | - | | |
| LinkExtend | | - | | |
| Linkspy | | - | | |
| LiveDic | | - | | |
| Locator | | - | | |
| Lovely forks | | - | | |
| Lowest Price Checker | | - | | |
| MSN for Firefox | | - | | |
| Map This | | - | | |
| Map With Google | | - | | |
| Map ＆ More | | - | | |
| Mark Ads Sites In Search | | - | | |
| Media Converter | | - | | |
| Media Player for YouTubeTM | | - | | |
| Media URL Timestamper | | - | | |
| MementoFox | | - | | |
| Miiverse | | - | | |
| Mini Map Sidebar Extension | | - | | |
| Mini Pixiv | | - | | |
| Mobile Wikipedia (WebExtension) | | - | | |
| Momiji Bookmark Button | | - | | |
| More Compact GMail | | - | | |
| Movie Critiques | | - | | |
| Moviesearcher | | - | | |
| MozTweak | | - | | |
| Multi Web Search | | - | | |
| Multi engine search | | - | | |
| Multifox | | - | | |
| My Contributions (crash report edition) | | - | | |
| My Map | | - | | |
| My Youtube | | - | | |
| NBA Scoreboard | | - | | |
| National Geographic Picture of the day | | - | | |
| Netograph | | - | | |
| NewLiveWall! | | - | | |
