Screengrab
Screengrab! saves webpages as images... but not for new versions of Firefox. FF changes too fast and I don't have the time to maintain it anymore. Bugs have developed that I am not in a position to investigate. Therefore, Screengrab is EOL.
6,434 users
FirePath
FirePath is a Firebug extension that adds a development tool to edit, inspect and generate XPath 1.0 expressions, CSS 3 selectors and JQuery selectors (Sizzle selector engine).
47,769 users
DNSQueries.com Toolbar
This toolbar integrates your browser and DNSQueries.com online tools, such as domain health check, dns query, traceroute, rbl (relay black lists), IP neighbors, SMTP tester, ping, DNS traversal and many more
54 users
Magic-Net Full Online DNS Lookup
DNS Search engine from Magic-NET. Full DNS records lookup, MX records lookup, Reverse lookup, PTR, rDNS, SPF records, Subdomains lookup, Multiple blacklist check, Zone Transfers.
0 users
Host Spy
On a shared hosting, HostSpy addon is a free useful tool to find out who current website's ip neighbors are.
179 users
View Source Chart
Enables accelerated human processing of DOM
3,728 users
WHOIS!
Lightweight WHOIS Lookup - Adds a small WHOIS button. For FireFox 3+ use Vitzo's WHOIS add-on instead: https://addons.mozilla.org/en-US/firefox/addon/10494
3 users
Modify Headers
Add, modify and filter the HTTP request headers sent to web servers. This addon is particularly useful for Mobile web development, HTTP testing and privacy.
44,799 users
RefControl
Control what gets sent as the HTTP Referer on a per-site basis.
44,039 users
Wappalyzer
Wappalyzer is a browser extension that identifies software on websites.
70,742 users
Capture Fox
You can capture your screen and record your voice to make screencasts (tutorials, e-lessons, etc.).
56 users
RFC search plugin
This plugin lets you search on RFC-editor.org database.
0 users
Pcapr search plugin
This plugin lets you search on Pcapr - www.pcapr.net - archive. Pcapr, powered by Mu Dynamics and called himself as a social nOtworking site, is a very large packet captures data base.
0 users
OVAL repository search plugin
This plugin lets you search on OVAL Repository.
0 users
Packet Storm search plugin.
This plugin lets you search on Packet Storm - www.packetstormsecurity.org - database. Packet Storm offers an abundant resource of up-to-date and historical security tools, exploits, and advisories.
0 users
Export All Certificates
Adds an option to export all root certificates.
242 users
CryptoFox
CryptoFox is an encryption/decryption tool for Mozilla Firefox, with dictionary attack support for cracking MD5 passwords.
486 users
Groundspeed
Groundspeed is an add-on that allows security testers to manipulate the application user interface to eliminate annoying limitations and client-side controls that interfere with the web application penetration tests.
550 users
JavaScript Debugger
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed. Venkman is the code name for Mozilla's JavaScript Debugger. Venkman aimed to provide a powerful JavaScript debugging environment for Mozilla based browsers.
47,219 users
Poster
A developer tool for interacting with web services and other web resources that lets you make HTTP requests, set the entity body, and content type. This allows you to interact with web services and inspect the results...
16,814 users
HTTP Resource Test
Firefox extension for testing HTTP Resources
1,792 users
RESTClient, a debugger for RESTful web services.
RESTClient has been completely rewritten for compatible with Firefox 57. Some functions are still missing (OAuth & OAuth 2.0 authentication).
106,001 users
URL Flipper
Quickly and easily increment and decrement numbers and strings in URLs for navigating through URL sequences.
1,979 users
Greasefire
Automatically find user scripts on Userscripts.org (requires Greasemonkey or Scriptish)
2,175 users
JSONView
View JSON documents in the browser.
49,063 users