Top 40 of Best Firefox Addons for Web Developers and Designers

Updated on August 1st, 2018 by Quertime Team in Web Development

Firefox is the best choice for anyone simply because its huge collection of free addons for every purpose, from automation to task management, documents syncing and FTP clients. Each of these addons can make certain things easier and that`s especially important for web developers and designers because searching for errors and optimizing your pages can be a painful and time-consuming process. Here are some of the best Firefox add-ons for anyone interested in web design or development. Most of them can be used to make your workflow quicker and more productive.

Firebug
Firebug integrates with Firefox to put a wealth of development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.

Web Developer
The Web Developer extension adds various web developer tools to a browser.

FireFTP
FireFTP is a free, secure, cross-platform FTP/SFTP client for Mozilla Firefox which provides easy and intuitive access to FTP/SFTP servers.

Greasemonkey
Greasemonkey allows you to customize the way a web page displays or behaves, by using small bits of JavaScript.

IE Tab
IE Tab is an extension from Taiwan, features: Embedding Internet Explorer in tabs of Firefox.

Stylish
Restyle the web with Stylish, a user styles manager. Stylish lets you easily install themes and skins for Google, Facebook, YouTube, Orkut, and other sites. You can even customize Firefox and other programs themselves.

Flagfox
Flagfox displays a country flag depicting the location of the current website’s server and provides a multitude of tools such as site safety checks, whois, translation, similar sites, validation, URL shortening, and more.

User Agent Switcher
The User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.

iMacros for Firefox
iMacros was designed to automate the most repetitious tasks on the web. If there’s an activity you have to do repeatedly, just record it in iMacros. The next time you need to do it, the entire macro will run at the click of a button! With iMacros, you can quickly and easily fill out web forms, remember passwords, create a webmail notifier, download information from other sites, scrape the web (get data from multiple sites), and more.

IE View
IE View lets you load pages in IE with a single right-click, or mark certain sites to *always* load in IE. Useful for incompatible pages, or cross-browser testing.

Screengrab
Screengrab! saves entire webpages as images. Just right-click on the page you want to grab and look in the “Screengrab” menu. It will capture what you can see in the window, the entire page, just a selection, a particular frame… basically it saves webpages as images – either to a file, or to the clipboard. It captures Flash too!

ColorZilla
With ColorZilla you can get a color reading from any point in your browser, quickly adjust this color and paste it into another program. You can Zoom the page you are viewing and measure distances between any two points on the page. The built-in palette browser allows choosing colors from pre-defined color sets and saving the most used colors in custom palettes. DOM spying features allow getting various information about DOM elements quickly and easily. And there’s more.

Clipmarks
Clipmarks lets you clip and share specific parts of articles, blog posts or anything else you read on the web. With the integrated Amplify service, you can post clips directly to Twitter or Facebook – or share them on clipmarks.com and more.

FireShot
FireShot creates screenshots of web pages entirely. The captures can be quickly annotated, saved to disk, copied to clipboard, printed, emailed and exported to external editor.

Tamper Data
Tamper Data lets you view and modify HTTP/HTTPS headers and post parameters. You can trace and time http response/requests as well as security test web applications by modifying POST parameters.

ShowIP
Show the IP address(es) of the current page in the status bar. It also allows querying custom information services by IP (right click) and hostname (left click), like whois, netcraft, etc. Additionally you can copy the IP address to the clipboard.

Live HTTP Headers
This addon allows you to view HTTP headers of a page and while browsing.

YSlow
YSlow analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages. YSlow is a Firefox add-on integrated with the Firebug web development tool. YSlow grades web page based on one of three predefined ruleset or a user-defined ruleset. It offers suggestions for improving the page’s performance, summarizes the page’s components, displays statistics about the page, and provides tools for performance analysis, including Smush.it™ and JSLint.

HTML Validator
HTML Validator is a Mozilla extension that adds HTML validation inside Firefox and Mozilla. The number of errors of a HTML page is seen on the form of an icon in the status bar when browsing.

MeasureIt
MeasureIt lets you draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.

JavaScript Debugger
Venkman is the code name for Mozilla’s JavaScript Debugger. Venkman aims to provide a powerful JavaScript debugging environment for Mozilla based browsers.

Quick Locale Switcher
Quick Locale Switcher allows you to quickly switch to a different language (User Interface, Spell Checker Dictionary and Website content) in your Mozilla application.

QuickJava
QuickJava allows quick enable and disable of Java, Javascript, Flash, Silverlight, Images, Stylesheets and Proxy from the Statusbar and/or Toolbar without having to open any dialogs!

Modify Headers
Modify Headers allows you to 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.

SeoQuake SEO extension
SeoQuake is a Firefox SEO extension aimed primarily at helping web masters who deal with search engine optimization (SEO) and internet promotion of web sites. Seoquake allows to obtain and investigate many important SEO parameters of the Internet.

SQLite Manager
This addon manages any SQLite database on your computer.

Console²
Console² (pronounced Console Squared or Console Two) replaces the JavaScript Console with what could be the next generation Error Console. From v0.5 includes the Console Filter extension previously available separately from the Console² website.

HttpFox
HttpFox monitors and analyzes all incoming and outgoing HTTP traffic between the browser and the web servers. It aims to bring the functionality known from tools like HttpWatch or IEInspector to the Firefox browser.

FirePHP
FirePHP enables you to log to your Firebug Console using a simple PHP method call. It is ideally suited for AJAX development where clean JSON or XML responses are required. All data is sent via response headers. This means that the debugging data will not interfere with the content on your page.

CSSViewer
CSSViewer shows the css parameters of any element in a web page, to enable/disable it simply click the toolbar icon.

EditCSS
EditCSS allows you to view all style sheets for the current page in the sidebar, make edits and see the result as you type.

Total Validator
Perform multiple validations and take screen shots in one go. This 4-in-1 validator works with external, internal, or local web pages using a local copy of the desktop tool.

Pixel Perfect
Pixel Perfect is a Firefox/Firebug extension that allows web developers and designers to easily overlay a web composition over top of the developed HTML.

FlashFirebug
Debug any AS3 SWF files on the web. Edit properties and inspect elements like you do to HTML. Redirect errors, warnings traces to the extension. This extension requires Firebug extension and Flash Player Debugger.

LinkChecker
LinkChecker helps you to check the validity of links on any webpage.

Aardvark
Aardvark is an user-friendly selector utility for selecting elements and doing various actions on them. It can be used for cleaning up a page prior to printing it (by removing and isolating elements), for making the page more readable, and (most appreciated by web developers), for analyzing the structure of a page.

CSS validator
Validates a page using the CSS Validator. Adds an option to the right-click context menu and to the Tools menu to allow for easy validation of the CSS of the current page. Opens the results in a new tab. It will only work on pages that have a CSS file associated.

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.

Font Finder
FontFinder is created for designers, developers and typographers. It allows a user to analyze the font information of any element on a page, copy any piece(s) of that information to the clipboard, and perform inline replacements to test new layouts.

Palette Grabber
Palette Grabber lets you create a color palette for Photoshop, Paint Shop Pro, GIMP, Flash, Fireworks, Paint.NET, or OS X based on the current page.

More Useful Firefox Addons for Web Developers and Designers