14 Essential Firefox Add-ons For Developers & Designers

Nowadays, the browser is the place to be. Our home. Whether we are developing, designing or managing projects.

Or simply browsing the web and consuming content. With the trend of browser-based web applications, many things take place in browser. And in most cases, Chrome is the preferred browser we use. Chrome offers an immense repository of extensions and developer tools.

Though there might be some disadvantages when using Chrome. More and more people report browser crashes and performance issues with Chrome. So you might consider Firefox as an alternative way to go.

In this post, I’m going to present you 14 of the best Firefox add-ons for developers and designers.

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Firefox or Firefox Developer Edition?

At the end of last year, Mozilla introduced a new browser explicitly designed for developers. So when switching to Firefox you might ask yourself if Firefox or the Firefox Developer Edition is the better choice.

The short answer to this question is: If you’re a developer or designer switching to Firefox you should definitely give the Developer Edition a try.

Why? Because it has some features which the regular Firefox version does not have (such as Web IDE or Valence). And most Firefox add-ons do work great in the Developer Edition as well.

So here they are. The best Firefox add-ons for developers and designers. Curated and hand-picked by the Usersnap web development team.

1. Usersnap

The Usersnap Firefox add-on lets you capture and annotate any web page. It works great for collecting and managing feedback on new mockups or website prototypes or for tracking bugs in your browser.

All created screenshots are directly saved in your projects which enable you to collaborate and discuss change requests or issues with colleagues and clients.

Usersnap Firefox Add-ons for developer


2. Web Developer

The Web Developer add-on for Firefox adds various web developer tools to your Firefox browser. I definitely recommend installing the Web Developer add-on since it gives you some great features which will definitely make your web development workflow faster.

I truly enjoy various CSS, form and image options which give you quick access and overview of the structure of the page.

The Web Developer add-on works great for both Firefox versions (the regular one and the Developer Edition).

Web Developer Firefox Add-ons


3. User Agent Switcher

The User Agent Switcher add-on for Firefox allows you to switch the user agent of a browser. The add-on will add new options to the tool settings for switching to Internet Explorer for example.

User Agent Switcher Firefox Add-ons


4. Firebug

Firebug is probably one of the best-known browser add-ons for Firefox. It offers you a wide range of development tools at your fingertips.

With the Firebug addon, you can edit, debug and monitor CSS, HTML, and JavaScript on any web page. Basically, it offers similar tools like the Firefox web developer tools, though many consider it as more user-friendly than the standard developer tools.

Important note: Firebug is not compatible with the latest release of the Firefox Developer Edition. Though it works seamless with the regular Firefox version.

Firebug Firefox Add-ons for developers


5. HttpFox

The HttpFox add-on is an HTTP analyzer for Firefox. It monitors all incoming and outgoing HTTP traffic between the browser and the web servers.


6. Ghostery

Ghostery is a great add-on available for Firefox (and other browsers as well) to display installed trackers, pixels and any other snippet on any website. Ghostery allows displaying those trackers which are collecting data on any given web page.

However, you can not only display those trackers, but you can also block them if you don’t want your sessions to be tracked.

Ghostery Firefox Add-ons for developers and designers


7. ColorZilla

ColorZilla is an advanced color picker and eyedropper. It allows you to get the color of any pixel in the browser window. The add-on is pretty simple and easy to use.


8. BuiltWith

As the name states, the built with Firefox add-on analyses website regarding the used technologies and software. It not only works great for analyzing competitor websites but basically allows you to take a look behind the scenes of any web page.


9. FireQuery

FireQuery is basically a Firefox add-on which adds new enhancements for jQuery to Firebug. It requires that Firebug has been installed and adds some improvements for jQuery.


10. Modify Headers

This Firefox add-on allows you to modify HTTP request headers sent to web servers. It is considered to be handy for mobile web development HTTP testing and privacy.


11. Advanced Cookie Manager

The Advanced Cookie Manager lets you monitor and manage the cookies. You can view, add, modify or even delete cookies in any of the domains. You can even export and import cookies which is super helpful when you have to reproduce certain issues by recreating certain browser sessions.


12. NoScript Security Suite

This Firefox add-on got quite some attention and is one of the top rated add-ons. It basically makes your browser experience safer by only allowing JavaScript, Java and other executable content to run only on trusted domains of your choice.


13. Dummy Lipsum

As a web developer or designer, you’ll find this extension quite helpful while working on new website mockups or prototypes. This Firefox add-on generates “lorem ipsum” text for your websites.


14. YSlow

This Firefox add-on analyses web pages regarding their performance based on various parameters. It gives you an overview on the performance including suggestions for improving your website.

YSlow requires Firebug to be installed since it runs “inside Firebug”.



We collected the most important information on those 14 Firefox Add-ons in this table below.

Firefox Add-onLast UpdateReviewsInstallations
Web DeveloperApril 29 2013228 reviews506.234 users
User Agent SwitcherJanuary 4 2011262 reviews342.133 users
FirebugMarch 30 20161.828 reviews2.180.026 users
HttpFoxMay 14 2014166 reviews88.925 users
GhosteryMarch 24 20161.297 reviews1.498.255 users
UsersnapMay 18 20151 review506 users
ColorZillaSeptember 3 2015306 reviews276.670 users
BuiltWithMay 26 20148 reviews9.044 users
FireQueryApril 21 201652 reviews25.979 users
Modify HeadersNovember 30 201174 reviews123.053 users
Advanced Cookie ManagerFebruary 22 201635 reviews36.917 users
NoScript Security SuiteApril 6 20161.568 reviews2.263.491 users
Dummy LipsumDecember 6 200942 reviews9.904 users
YSlowAugust 26 2013204 reviews86.493 users

That was a lot.

Wow…that was definitely a lot. If you just made the switch back to Firefox you might be impressed by the number of available add-ons. Firefox is definitely a powerful browser with a broad range of features, add-ons, and tweaks. With the mentioned add-ons you can modify and customize your experience when using Firefox.

Any great Firefox add-on for developers and designers missing? Let us know in the comments!

PS: If you prefer a short summary of the best Firefox add-ons for developers & designers we got you covered.

This article was brought to you by Usersnap – a visual bug tracking tool for every web project. Used by software companies, like Facebook, AddThis, and Google.

manage web projects - usersnap

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