Zen
Free Firefox-based browser with vertical tabs, Spaces, Essentials, Glance and split view. Imports Arc.
Zen is a free, open-source fork of Firefox with a vertical sidebar, workspaces (Spaces), pinned tabs and folders, Essentials, Glance link previews and split view. Version 1.24b (October 2026) added an Arc importer for Spaces, pinned tabs, folders and profiles, and a Dia importer for browser data (not Dia pinned tabs). It installs Firefox add-ons rather than Chrome extensions, and it has no Google Widevine licence, so Netflix and Spotify do not play on Windows and macOS. The project calls itself beta and is built by a small volunteer team funded by donations.
Built-in AI
No AI
No Zen-built AI. Firefox chat sidebar, shortcuts, link previews and ML are pinned off in Zen default prefs.
github.comBloat check
None found
No ads, wallet, feed or upsells; sponsored suggestions are locked off, and telemetry and the crash reporter are compiled out.
github.comAds, crypto, paid upsells, news feeds, default-on telemetry, required accounts.
Organization
| Feature | Zen | Arc | Note |
|---|---|---|---|
| SidebarVertical sidebarTabs live in a vertical sidebar that is the main tab UI and can be hidden. | ✓ | ✓ | Vertical tabs are the core design; horizontal tabs are not planned.docs.zen-browser.app |
| SpacesSeveral workspaces per window, each with its own pinned and open tabs, switched by swipe or shortcut. | ✓ | ✓ | Workspaces with their own tabs and pinned tabs, switched by shortcut or swipe.docs.zen-browser.app |
| ProfilesProfiles per Space (shareable)Each Space can use its own browser profile (separate cookies, logins, history), and one profile can be shared by several Spaces. | ◐ | ✓ | Each Space can use a Firefox container (cookies/logins only; history and extensions shared); Spaces can share one.github.com |
| FavoritesGlobal favoritesPinned icons at the top of the sidebar shared by every Space (Zen calls them Essentials). | ✓ | ✓ | Called Essentials; shared across Spaces, but split per container by default (separate-essentials pref).github.com |
| Pinned TabsPinned tabs & foldersPer-space pinned tabs that act like bookmarks, with nested folders. | ✓ | ✓ | Per-space pinned tabs; nestable folders added in 1.15b.zen-browser.app |
| Live foldersSidebar folders that fill and refresh themselves from an outside source, such as GitHub pull requests or an RSS feed. | ✓ | ✓ | Live Folders refresh every 30 min by default from RSS/Atom feeds or GitHub pull requests and issues.github.com |
| ArchiveAuto-archive tabsUnpinned tabs close automatically after a set time and stay recoverable in an archive. | ◐ | ✓ | Firefox tab unloader frees idle tabs (time/memory); Clear Tabs button; no archive or timed close in code.github.com |
| Theme pickerSpace themesPer-space colour or gradient themes. | ✓ | ✓ | Per-workspace gradient themes with a colour picker and grain options.zen-browser.app |
Browsing
| Feature | Zen | Arc | Note |
|---|---|---|---|
| Split ViewTwo or more tabs side by side in one window. | ✓ | ✓ | Up to 4 tabs side by side in horizontal, vertical or grid layouts.docs.zen-browser.app |
| PeekLink previewOpen a link in an overlay without leaving the current page (Zen calls it Glance). | ✓ | ✓ | Called Glance; Alt+Click by default, expandable into a tab or split view.docs.zen-browser.app |
| Little ArcMini windowA small, chrome-less window for links opened from other apps or a quick search. | ✕ | ✓ | Open feature request; external links open as normal tabs, Glance is an in-window overlay.github.com |
| Command barA ⌘T palette that searches tabs, history, bookmarks and browser commands. | ✓ | ✓ | New Tab opens a floating URL bar that searches tabs, folders, history and bookmarks and runs commands.zen-browser.app |
| Air Traffic ControlLink routingRules that send links from other apps to a chosen space or profile. | ✓ | ✓ | Space Routing: URL rules (incl. regex) send links to a Space, plus a default route for external links.github.com |
| BoostsSite customizationPer-site custom CSS/JS, or zapping elements off a page. | ✓ | ✓ | Boosts (since 1.20b): per-site colours, fonts, styles, zap and dark mode; shareable since 1.24b.linuxiac.com |
| Auto PiPAuto picture-in-picturePlaying video pops out into picture-in-picture automatically when you switch tabs. | ✓ | ✓ | Settings checkbox "Keep playing videos in Picture-in-Picture when switching tabs" (Firefox 160 base); Zen ships it off.github.com |
| Mini playerMedia still playing in a tab you left keeps play/pause controls in the sidebar. | ✓ | ✓ | Sidebar media cards with play/pause, previous/next, mute and PiP for tabs playing media; on by default.github.com |
| Tab SwitcherRecent-tab switcherCtrl+Tab jumps back to the tab you used last and cycles in recently used order. | ✓ | ✓ | Firefox's Settings > Tabs & Browsing checkbox "Ctrl+Tab cycles through tabs in recently used order" is kept; Zen patches ctrlTab for it. Off by default.github.com |
| Super CopyClean link copyA shortcut (⌘⇧C) copies the page URL with tracking parameters removed. | ✓ | ✓ | Ctrl/Cmd+Shift+C copies the URL through Firefox's tracking-parameter stripper. On dev, several selected tabs copy all their clean URLs (not yet in 1.24.2b).github.com |
| CaptureScreenshotsBuilt-in capture of a chosen area or element, and of the full page. | ✓ | ✓ | Firefox Screenshots, kept and listed in Zen's command bar: drag or click a region, or Save visible / Save full page.github.com |
Compatibility & migration
| Feature | Zen | Arc | Note |
|---|---|---|---|
| Arc importImports Arc spaces, pinned tabs and folders. | ✓ | – | Since 1.24b: Spaces, pinned tabs, folders and Favorites as Essentials; extra Arc profiles become containers.github.com |
| Chrome extensionsInstalls extensions from the Chrome Web Store. | ◐ | ✓ | Firefox add-ons only (addons.mozilla.org); the Chrome Web Store is not supported.docs.zen-browser.app |
| DRM streamingNetflix, Disney+, Spotify web and other DRM video/audio play, through Widevine or, on WebKit, FairPlay. Chromium forks need a Google Widevine licence; FairPlay counts once a major service is confirmed playing in the app. | ✕ | ✓ | Widevine is built in but unlicensed (FAQ): DRM sites fail on Windows/macOS. The team said on 2026-11-13 DRM is coming "very soon"; no build has it yet. Linux streams (HowToGeek).docs.zen-browser.app |
| PasskeysWebAuthn passkeys, Touch ID and the system/iCloud keychain. | ✓ | ✓ | Passkeys on macOS since 1.10b; release builds carry Apple's passkey entitlement and a provisioning profile.github.com |
| SyncSpaces, pinned tabs and settings sync across devices. | ✓ | ✓ | Mozilla account sync; Spaces/folders since 1.22b via a Settings > Sync toggle (off by default), tabs optional.github.com |
| Mobile appiPhone, iPad or Android app that shares spaces with desktop. | ✕ | ◐ | No Android or iOS app and none planned.docs.zen-browser.app |
Extras
| Feature | Zen | Arc | Note |
|---|---|---|---|
| Built-in ad blockerAd and tracker blocking without installing an extension. | ◐ | ✓ | Onboarding pre-selects installing uBlock Origin (1.22.1b+); no built-in blocker beyond Firefox tracker blocking.github.com |
| Custom ShortcutsShortcut editorMost browser keyboard shortcuts can be remapped in Settings. | ✓ | ✓ | Settings has a Keyboard Shortcuts entry opening Firefox's about:keyboard, extended with Zen's own shortcuts; Firefox and Zen keys can be recorded, cleared or reset.github.com |
More Arc features
Arc features shown but not counted in the score, because almost no replacement has them or only a few people need them.
| Feature | Zen | Arc | Note |
|---|---|---|---|
| EaselsA shareable canvas of live page captures, notes and drawings. | ✕ | ◐ | No easel or canvas code under src/zen at bf360bf; Easels exist only as a feature request (discussion #4290).github.com |
| Shared CollectionsShared spaces & foldersShare a Space, folder or set of tabs as a link anyone can open, or another user can add to their sidebar. | ✓ | ✓ | Right-click Share Space or Share Folder uploads tabs to share.zen-browser.app and copies a link that opens, with Add to Zen, in another Zen.github.com |
| PreviewsWeb app previewsHover a pinned Gmail, Calendar or other web app to glance at it; a pinned calendar shows the next meeting with Join. | ◐ | ✓ | Only an unread dot on Essentials whose title starts with a count like "(3)"; on in Twilight 1.25t, off in 1.24.2b. No hover glance or calendar.github.com |
| Developer modeA developer view that turns on by itself for localhost: full URL, quick DevTools and dev tools in reach. | ✕ | ✓ | Only standard Firefox DevTools and its JSON viewer; no developer mode or localhost handling in src/zen.github.com |
Extension support
Which extension formats and stores run, beyond the Chrome Web Store row above.
| Feature | Zen | Arc | Note |
|---|---|---|---|
| Manifest V2 extensionsThe older extension format Chrome removed in 2025. Needed for full uBlock Origin and other extensions that block requests. | ✓ | ✕ | Firefox 160 keeps MV2 and blocking webRequest; Zen patches neither, so full uBlock Origin works.blog.mozilla.org |
| Manifest V3 extensionsThe current extension format used by the Chrome Web Store (and supported by Firefox and Safari). | ✓ | ✓ | Firefox 160's manifest schema accepts MV3 (event pages, no service workers); Zen does not patch it.github.com |
| Firefox add-onsAdd-ons from addons.mozilla.org or .xpi files install and run. | ✓ | ✕ | Installs add-ons from addons.mozilla.org per the docs; Firefox themes are not supported.docs.zen-browser.app |
| Safari extensionsSafari web extensions (the App Store extension apps Safari uses) install and run. | ✕ | ✕ | Gecko-based: runs only add-ons from addons.mozilla.org; no Safari web extension support.docs.zen-browser.app |