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Web Developer vs Firefox Developer Tools: catalog facts
Web Developer	Firefox Developer Tools
Free Free and open source under the GPL.	Free Free and included with Firefox.
Browser extension	Windows, macOS, Linux
Dozens of page manipulations one click away, many still missing from devtools Same toolbar across Chrome, Firefox and Edge	Built into Firefox with nothing extra to install Can debug Firefox for Android remotely
Much of its original value is now covered by built-in developer tools Interface is a dense menu-driven toolbar	Only available inside Firefox Tests Firefox's engine, so other browsers still need their own tools
Browser extension	Downloadable app
Open source	Open source
License: GPL-3.0	License: MPL-2.0
Not stated if an account is needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.