Best Firefox Add-ons for Web Designers (2026)

Firefox is still a favourite browser for web designers, thanks to excellent built-in developer tools and a solid add-on library. Our 2010 list of Firefox add-ons for web designers featured Firebug, IE Tab, YSlow and GridFox, all of which have since been retired or built into the browser. Here’s the updated toolkit for 2026.

Quick answer: Start with Firefox’s built-in DevTools (Inspector, CSS Grid and Flexbox inspectors, Responsive Design Mode, eyedropper and screenshots), then add Web Developer, ColorZilla, Fonts Ninja, Wappalyzer and axe DevTools. Together they cover layout, colours, fonts, technology checks and accessibility.

Built-in Firefox tools that replaced old add-ons

• Firefox DevTools (press F12) replaced Firebug, which was discontinued. Inspect and edit HTML and CSS live, and debug JavaScript.
• Storage Inspector replaced Firecookie for viewing and editing cookies and local storage.
• CSS Grid and Flexbox inspectors overlay your layout grid, replacing GridFox.
• Responsive Design Mode (Ctrl+Shift+M) previews your design at phone and tablet sizes.
• Eyedropper picks any colour on the page.
• Screenshots: right-click a page and choose Take Screenshot to capture an element or the full page.
• Font panel in the Inspector shows which fonts an element uses.

Best Firefox add-ons for web designers

1. Web Developer

Web Developer by Chris Pederick adds a toolbar to disable CSS, outline elements, show image sizes, view alt text and much more. A classic that’s still maintained.

2. ColorZilla

ColorZilla is an advanced colour picker with a palette history and a CSS gradient generator.

3. Fonts Ninja

Fonts Ninja identifies fonts on any website with one click, showing size, weight and line height.

4. Wappalyzer

Wappalyzer shows the CMS, frameworks, analytics and other technologies a site uses. Handy when a client says “make it like this site”.

5. axe DevTools

axe DevTools adds accessibility checks to Firefox DevTools, flagging contrast, missing labels and other issues.

What happened to the 2010 picks?

• IE Tab: Internet Explorer is retired. Test in real Chrome, Safari and Edge, or use a cross-browser testing service.
• YSlow: use Google PageSpeed Insights and Firefox’s Performance panel instead.
• Aardvark and Palette Grabber: no longer available; DevTools and ColorZilla cover most of their features.

Tips for using design add-ons

• Install only what you use; too many add-ons slow the browser.
• Check permissions, since design add-ons can read every page you visit.
• Create a separate Firefox profile for design work to keep your main browser clean.
• Try Firefox Developer Edition for early access to new DevTools features.

Originally written by guest author Sonia Mansfield, content editor for PsPrint.com. Updated for 2026 by QuickOnlineTips.

FAQ

Is Firebug still available?

No. Firebug was discontinued, and its features are built into Firefox DevTools.

What is the best Firefox add-on for web designers?

Web Developer is the most versatile, with ColorZilla for colours and Fonts Ninja for fonts.

Do Firefox add-ons work in Firefox Developer Edition?

Yes, Developer Edition supports the same add-ons as regular Firefox.