| Image Map Editor | | - | | |
| IE NetRenderer | | - | | |
| HttpRequester | | - | | |
| Html Validator | | - | | |
| Holmsie | | - | | |
| HackBar | | - | | |
| HTTP Resource Test | | - | | |
| HTMLEditor | | - | | |
| HTML Regex Data Extractor | | - | | |
| HTML Element Detector | | - | | |
| HTML Color Coder | | - | | |
| HTML 5 Validator | | - | | |
| GridFox | | - | | |
| Graphical Timeline of Events | | - | | |
| Good Website Inspector | | - | | |
| Generic CSS Loader 2 | | - | | |
| Fresh Dom Tree View | | - | | |
| Fresh CSS | | - | | |
| Foxy SEO Tool | | - | | |
| Foxy Detective | | - | | |
| Force CORS | | - | | |
| Fontface Ninja | | - | | |
| Font Inspector | | - | | |
| Font Finder(737353) | | - | | |
| Font Finder | | - | | |
| Flashlight | | - | | |
| Flashbug | | - | | |
| FlashFirebug | | - | | |
| Firepicker | | - | | |
| Firefox Accessibility Extension | | - | | |
| Firefinder for Firebug | | - | | |
| Firebug Paint Events | | - | | |
| Firebug Autocompleter | | - | | |
| Firebug | | - | | |
| FireXPath | | - | | |
| FireStorage Plus! | | - | | |
| FireStorage | | - | | |
| FireSSH | | - | | |
| FireRuler | | - | | |
| FireRainbow | | - | | |
| FireQuery | | - | | |
| FireMobileSimulator | | - | | |
| FireHiddenView | | - | | |
| FireFontFamily | | - | | |
| FireDiff | | - | | |
| FireClosure | | - | | |
| Extinctor | | - | | |
| Extension source viewer | | - | | |
| Extension Developer | | - | | |
| Execute JS | | - | | |