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Safari Technology Preview vs Firefox Nightly: catalog facts
Safari Technology Preview	Firefox Nightly
Free Free download from Apple.	Free Free and open source.
macOS	Windows, macOS, Linux
Latest WebKit engine ahead of stable Safari Runs side by side with regular Safari	Earliest access to new Firefox features Updated daily
macOS only Pre-release software that may be less stable	Pre-release builds can be unstable Not suited as a main browser for most people
Downloadable app	Downloadable app
Closed source	Open source
License not stated	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
Official website Full listing and sources Checked September 24, 2026	Official website Full listing and sources Checked September 24, 2026

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