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BasiliskFirefox ESR
Free

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

 Free

Free and open source; Mozilla offers optional paid professional support for organisations.

Windows, macOS, Linux Windows, macOS, Linux
  • Runs classic XUL extensions that no current browser supports
  • Independent of Chromium and of current Firefox
  • Long-term stable feature set for managed deployments
  • MSI and PKG installers plus group policy templates
  • Small development team, so security fixes and web compatibility lag
  • Many modern sites do not work correctly
  • New features arrive later than in regular Firefox
  • Mainly aimed at organisations rather than home users
Downloadable app Downloadable app
Open source Open source
License: MPL-2.0 License: MPL-2.0
Not stated if an account is needed No account needed
Not stated if it works offline Not stated if it works offline

Checked September 22, 2026

Checked September 24, 2026

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