Tabs pile up faster than a strip across the top of a window can show them, and Arc’s sidebar fixed that until its makers stopped adding features. Zen Browser takes the same idea to Firefox: a free, open-source web browser for Windows, macOS, and Linux that trades the tab bar for a vertical sidebar and separate Workspaces. Before you commit to the Zen Browser download, one question is worth settling. Can it be your only browser, or will it end up as the pretty second one?
Can Zen Browser replace Arc without moving to Chromium?
Zen Browser is the closest free, cross-platform match for the Arc way of working, and it runs on Mozilla’s Gecko engine instead of Google’s. Tabs live in a left sidebar, projects split into separate Workspaces, and Compact Mode hides the interface until the cursor reaches the edge of the screen. Because the base is Firefox, uBlock Origin and the rest of the Firefox add-on catalog work normally, and Firefox security fixes reach Zen soon after Mozilla ships them. The Zen Browser Team moves quickly on its own features too: recent updates added a new onboarding flow, quicker Space creation, reorderable containers, and local profile backups that restore across all three desktop systems.
The catch comes with the same choice. Leaving Chromium means leaving the Chrome Web Store, and on Windows and macOS it means Netflix and Spotify will not play in the browser at all. For anyone who streams in a browser tab every evening, that outweighs any layout gain. Zen Browser is the best free way to browse Arc-style without Chromium, as long as a second browser stays installed for streaming on Windows or macOS.
Fewer stray tabs with Workspaces, Glance, and Split View
Workspaces keep a separate set of tabs for each project, so a research session does not bury the tabs used for everyday work. Firefox containers sit alongside them and keep logins apart, which lets a work account and a personal account stay signed in to the same site at once. Essentials are pinned favorites at the top of the sidebar, a natural home for mail and calendar. Glance opens a link as a floating preview over the current page, so a search result can be read and dismissed without leaving another tab behind.
Split View puts several tabs side by side: select them with Ctrl or Shift, right-click, and choose to split them. Zen Mods, installed from the built-in theme store, reshape the interface with floating address bars, slimmer sidebars, and custom colors, and anyone comfortable editing userChrome.css can go further. Firefox Sync works through a Mozilla account and carries bookmarks, passwords, history, and add-ons between computers.
One habit takes adjusting. Vertical tabs are the foundation of the whole design, and the team has said a traditional horizontal tab strip is not planned for the near future.
How moving in from Arc or Chrome works
The onboarding flow offers to import bookmarks, browsing history, and saved passwords from another browser on the same computer, so the switch does not start from an empty sidebar. Taking that offer during setup saves a manual password export later. Extensions are the part that does not move. Chrome add-ons will not install, so the practical first job is checking that each must-have tool has a Firefox version. Well-known password managers and ad blockers generally publish Firefox versions, so the less common tools on the list are the ones to check before switching. Arc users will find the vocabulary familiar, since Spaces map to Workspaces and pinned tabs map to Essentials. Setting up two Workspaces in the first session is the quickest way to learn whether the sidebar model fits your day.
Streaming, mobile, and build limits to check first
Zen Browser cannot play DRM-protected streams on Windows or macOS, because the project has no Widevine license from Google. That rules out these services in the browser:
The Linux build is not affected. The limit is also easy to misread: Zen reports Widevine support to websites, yet the license handshake with streaming services still fails, so a quick browser check can say DRM is available while Netflix still refuses to play.
There is no Android or iOS version either, and the team has said the vertical-tab design does not translate well to phones. Firefox on a phone, synced through the same Mozilla account, fills that gap for bookmarks and passwords. The build names can confuse newcomers too. Twilight builds are pre-release versions with experimental changes, while the regular release is the steadier choice for daily use even though it still carries a beta label.
Zen Browser compared with Arc, Floorp, and Firefox
Arc still has the most polished take on this layout and runs every Chrome extension, but it is built on Chromium, its makers have moved their attention to a newer browser, and it offers no Linux version. Floorp shares Zen’s Firefox base and privacy stance but takes the opposite approach to design: it is more modular, with dual sidebars, web panels for apps, and support for installing sites as web apps, while Zen ships more opinionated and quicker to learn. Firefox itself now offers vertical tabs and tab groups, and it keeps one advantage Zen cannot match yet, a Widevine license, so streaming simply works.
Zen is the pick for the calmest Workspace setup on Gecko, while Floorp suits people who want to rebuild the interface piece by piece. Anyone who streams inside the browser should stay with Firefox, and Arc only makes sense when Chrome extensions matter more than avoiding Chromium.
Gecko engine speed and memory use in daily browsing
Page loading tracks Firefox closely, since both run the same Gecko engine and Zen moves to each new Firefox base soon after release. Firefox-based web browsers generally hold less memory than Chromium web browsers with a similar tab count, which is one practical reason to choose Zen over Arc on an older laptop. Recent releases cut CPU spikes and disk writes caused by session saving, and that matters for anyone who keeps a large session open for days. Linux has also picked up memory and performance improvements from newer Firefox bases. On Windows machines with an NVIDIA RTX card, RTX Video Super Resolution can be switched on through about:config for sharper video playback.
Deciding if Zen Browser earns a place on your desktop
Former Arc users and people already comfortable with Firefox add-ons get the most from Zen Browser, since the Workspace sidebar is the whole point and the add-on catalog comes along unchanged. Anyone tied to Chrome-only extensions, or who does most of their streaming in a browser tab on Windows or macOS, should hold off for now. For everyone else, the Zen Browser download is worth making, and keeping a separate streaming browser on the side costs nothing.
