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VisBugFirefox Developer Tools
Free

The open-source extension is available without a license fee.

 Free

Free and included with Firefox.

Web, Browser extension Windows, macOS, Linux
  • Edit spacing, type and colour on a live page without touching developer tools
  • Measurement and accessibility inspection built into the same toolbar
  • Built into Firefox with nothing extra to install
  • Can debug Firefox for Android remotely
  • Changes are temporary and vanish on reload
  • Complex layouts can behave unpredictably when dragged
  • 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: Apache-2.0 License: MPL-2.0
Not stated if an account is needed No account needed
Not stated if it works offline Works offline

Checked September 22, 2026

Checked September 23, 2026

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