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SigmaOS vs Zen Browser: catalog facts
SigmaOS	Zen Browser
Freemium A free tier is available. Heavier use moves to a paid subscription.	Free Free and open source, funded by donations.
macOS	Windows, macOS, Linux
Tabs live in named workspaces with separate logins, and each one can be marked done or locked, which…	Vertical tabs, workspaces and split view built in, no extensions needed Firefox engine, so Firefox extensions and containers work
It is closed source, macOS-only, and the free tier is limited enough that regular use pushes you to…	Young project; interface changes between releases and bugs surface A small team maintaining a Firefox fork is a real long-term risk
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	Needs internet
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked September 21, 2026

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