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Firefox tools to help web application testing and development

There has been several blogs that lists the best Firefox extensions that are out there. Since Pingdom are operating in the web performance and monitoring field we decided to make our own list of valuable Firefox extensions.

In this list we don’t cover the well known extensions such as Web Developer Toolbar and Firebug but rather focused on “lesser known” ones that can help development and testing. Extensions that deal with HTML, CSS, SEO and design were also ignored since other blogs have already made good lists of these kinds of tools.

Let’s get on to the list.


YSlow has received great attention which is hardly a surprise since it’s such a good tool. It can analyze web sites and give you information about all requests that are made, load time, component sizes and also give you tips on how you can improve the speed of your web site. This extension requires that Firebug is installed.


Jiffy Firefox Extension

Jiffy is a new extension which gives a more detailed view of Javascript time measurements. You can get information of AJAX requests and other Javascript functions. The extension is based on Jiffy-Web Suite. This extension requires that Firebug is installed.



Using Firecookie you can view and manage cookies. It also has a console where you can see when cookies are created, changed or deleted. This extension requires that Firebug is installed.


Live HTTP Headers

Live HTTP Headers as the name says lets you view the headers sent by the web server. This can be useful when debugging web applications. It also lets you edit request headers and replay a request.



HttpFox monitors and analyzes all incoming and outgoing http traffic between the browser and the web server. It displays all request and response headers, sent and received cookies, querystring parameter, POST parameters and response body.



Poster is a tool for interacting with web services and other web resources and analyze the result. You can make HTTP requests and edit the body and content type and then inspect the result.


DNS Cache

This extension lets you easily disable and enable the DNS Cache in Firefox.



TestGen4Web is a tool that lets you record actions in Firefox to a XML file which can later be played back. The output can also be translated into formats so the recorded tests can be processed in other software as automated test scripts.


Selenium IDE

Selenium is a test tool for web applications where Selenium IDE is the recorder, much like TestGen4Web. It can record and playback actions and save the recordings as different scripts.


For more Firefox extensions for web development and design, see the following blogs:

  • Top Best 50 Firefox Extensions for web design
  • 10 Must Have Web Development Firefox Extensions
  • 30+ Firefox Add-ons for Web Developers & Designers


We all need Mr Uptime for Firefox 3. Wonderfull tool...

Michael Boggs
Michael Boggs

Still no word on Mr. Uptime being made to work with firefox 3?


he is -regarding his little head - BIG BIG useful guy, not little! Please update him!

Andrew from Vancouver
Andrew from Vancouver

I was wondering the same thing; as of this writing, Mr. Uptime is disabled by Firefox 3. And the site is still advertising Firefox 2... Please update Mr. Uptime, he's a useful little guy!

Michael Boggs
Michael Boggs

Speaking of firefox extensions, when will Mr. Uptime be updated so I can use it with FireFox 3?


jardel: We feel that MR Uptime is not directly focused on development or testing but rather a useful tool for everyone.

Frank Cohen
Frank Cohen

Thanks for publishing this list. The tools you chose are excellent. Your readers may be interested in PushToTest TestMaker too. TestMaker is the open source test (OST) platform that turns TestGen4Web and Selenium tests into functional tests, load and performance tests, and business service monitors. TestMaker provides a Data Production Library (DPL) system to provide operational data to tests at test runtime, including data from CSV files and RDBMS queries. Details are found at -Frank


where's mr uptime?


This extensions are indeed a must for every web developer, can sometime make your life easier.


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