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JSON Viewer vs Firefox Developer Tools: catalog facts
JSON Viewer	Firefox Developer Tools
Free Free and open source under the MIT licence.	Free Free and included with Firefox.
Browser extension	Windows, macOS, Linux
API responses become readable in place, with collapsible nodes Raw view remains available for copying	Built into Firefox with nothing extra to install Can debug Firefox for Android remotely
Chromium browsers only; Firefox has a built-in JSON viewer	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: MIT	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.