| Firefox DNS Flusher | | - | | |
| Flag ＆ IP Address ＆ Domain WHOIS Info | | - | | |
| Flagfox | | - | | |
| Flash Video Downloader - Youtube Downloader | | - | | |
| FlashGot | | - | | |
| Force-TLS | | - | | |
| FormFox | | - | | |
| FoxyPAC | | - | | |
| FoxyProxy | | - | | |
| FoxyProxy Basic | | - | | |
| FoxySpider | | - | | |
| Furaffinity Download extension | | - | | |
| GA? | | - | | |
| Googley Eyes | | - | | |
| HTTP Header | | - | | |
| HTTP Header Live | | - | | |
| HTTP Request Logger | | - | | |
| HTTP Response Browser | | - | | |
| HTTP Tool | | - | | |
| HTTP request maker | | - | | |
| HTTP-Nowhere | | - | | |
| HTTPS Finder | | - | | |
| HTTPS Percentage | | - | | |
| HTTPS-Everywhere | | - | | |
| Header Editor | | - | | |
| Header Spy | | - | | |
| HeaderTool | | - | | |
| Heuristic Network Prefetcher | | - | | |
| Hide My Ass! Web Proxy | | - | | |
| HostAdmin | | - | | |
| HostIP.info Geolocation Plugin | | - | | |
| HttpFox | | - | | |
| IDND | | - | | |
| IMPAS | | - | | |
| IP Flager | | - | | |
| IP Kingdom | | - | | |
| IPLogger | | - | | |
| IPvFox | | - | | |
| Image Download Ⅱ | | - | | |
| ImageHost Grabber | | - | | |
| InlineDisposition | | - | | |
| InlineDisposition (WebExtensions) | | - | | |
| InlineDisposition 2 | | - | | |
| Insight | | - | | |
| Irvine ContextMenu | | - | | |
| Is it up? | | - | | |
| Key Manager | | - | | |
| Link Evaluator | | - | | |
| Link Extractor | | - | | |
| Link Gopher | | - | | |
