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Waterfox vs Mercury: catalog facts
Waterfox	Mercury
Free Free and open source under MPL-2.0. Development is funded by donations.	Free Free and open source.
Windows, macOS, Linux	Windows, macOS, Linux
Telemetry and data collection are removed from the build, not just disabled in preferences Ad blocking and private, anonymised DNS are on by default	Compiler-optimized Firefox builds Privacy patches drawn from LibreWolf, Waterfox and IceCat
One small team tracking Mozilla, so security updates land after Firefox's The project has changed hands in the past, which matters if you are picking it on trust	Maintained by a single developer Updates can trail official Firefox releases
Downloadable app	Downloadable app
Open source	Open source
License: MPL-2.0	License: MPL-2.0
No account needed	No account needed
Needs internet	Not stated if it works offline
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked September 23, 2026

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