8 of the Best Firefox Add-ons for Web Development

Firefox’s market share has declined in recent years mainly due to the rise of Google Chrome and some questionable changes to the browser infrastructure by the Mozilla Foundation.

However, its large offering of useful add-ons web security features remain appealing to many users who have refused to join the Chrome bandwagon.

For web developers who have decided to stick with Firefox, we have compiled a list of some of the best add-ons that should ease your development workflow by a considerable amount. Tell us what you think in the comments section at the end of the article.


BuiltWith is a superb extension that allows you to view the exact technologies that are used to develop various websites. Once you install the extension, an icon will be added to your toolbar that you can click on at any time when browsing to view the underlying infrastructure of any website.


You do not necessarily need an add-on to switch the user agent of your browser, but the process of doing so is quite tedious. The User Agent Switcher extension does all the heavy lifting for you by adding a menu and toolbar icon that allows you to choose from pre-configured user agents or add new ones.


Greasemonkey is one of the most popular extensions for Firefox. It allows you to change the way a website behaves by injecting JavaScript onto a page. The changes will be enforced every time you open that particular website without any further input on your part.


JSON View enhances your development experience by allowing you to view JSON files in your browser with proper formatting, syntax highlighting and object/array collapsing. Even if the document contains errors, JSON View will still render the file in plain text.


Minified JavaScript files are often used in production to reduce bandwidth consumption and aid the speed and responsiveness of a website. However, they are impossible to read by humans, so one must unminify it first before any type of debugging can be carried out. JS Deminifier uses the algorithm from jsbeautifier.org to format and beautify the JavaScript that loads in your browser so that you can read and carry out debugging operations easily.


HTTPFox integrates with Firefox to provide seamless HTTP monitoring without leaving the browser window. Basically, it allows you to monitor the incoming and outgoing HTTP traffic between your browser and a web server.


FlagFox is a very neat extension which should appeal to web security enthusiasts and developers alike. It displays a flag icon in the address bar indicating the current web server’s physical location and provides other tools for checking Whois and DNS information, Alexa ranking, server status, server testing and much more.


Awesome Screenshot Plus is an extremely useful add-on that can capture any part of a webpage, and even the entire page if you so desire. Once you capture a screenshot, it will be displayed in a separate tab where you can perform some basic editing before saving. It supports saving the screenshots to disk as a JPG or PNG image as well as uploading to Google Drive.

The following popular web development add-ons were not included in this article because they have already been covered in a separate article written a while ago.

If we left out your favorite Firefox extension for web development, tell us about it in the comments section and share the other ways you like to optimise Firefox to achieve a better development or debugging workflow.