Zen

Zen is a desktop web browser built on Firefox's Gecko engine, arranged around vertical tabs and named workspaces instead of the horizontal tab bar most browsers still default to. It runs natively on Linux, which matters because its closest design inspiration never shipped one.

Why Zen instead of Arc

Arc popularized the vertical sidebar, named "Spaces," split view and pinned favorites — then its maker, The Browser Company, stopped shipping new features and never released a Linux build. Zen rebuilds that layout — sidebar tabs, workspaces instead of Spaces, split view, pinned "Essentials" — on Firefox instead of Chromium, so it installs anywhere Firefox does, Linux included.

The practical difference shows up in daily operation more than in price, since Arc was already free. Zen ships as a Firefox fork with point releases tied to upstream Firefox versions, so security patches land on the same cadence Firefox users already trust. There's no sign-in wall to start browsing, unlike Arc's early login requirement, and because the engine is Gecko rather than Chromium, extensions like uBlock Origin keep full filtering power instead of the reduced Manifest V3 rules Chromium browsers now enforce.

What it does well

• Vertical tab sidebar shows full page titles even with dozens of tabs open, and can collapse to icon-only or auto-hide for a compact layout that gives the page the entire window width.
• Named workspaces isolate groups of tabs by color or emoji and can bind to a separate container profile, so a work login and a personal one never share cookies.
• Split view tiles up to four tabs into a grid inside one window, handy for comparing two documents without a second monitor.
• Glance opens a linked page in a floating preview panel so a reader can check it without losing the current tab.
• Runs the full Firefox extension catalog, including content blockers that Chromium's newer extension rules limit elsewhere.
• HTTPS-Only mode, OCSP certificate checks and Firefox's phishing and malware filters carry over from upstream unchanged.
• Builds for Linux, Windows and macOS from one codebase, so a saved workspace layout looks the same across machines.

Limitations

• Contributors have opened GitHub issues about telemetry, arguing that data-collection settings ship enabled by default and asking maintainers to publish exactly what fingerprinting protection is active rather than rely on a "privacy-focused" label.