Verified Sep 2026

ActiveGecko engine 29/30 documented

Zen Browser

A Firefox-based browser focused on compact vertical navigation, workspaces, and customization.

Published by Zen Browser contributors (International) · Verified September 2026

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Runs on

macOSmacOS: Available
WindowsWindows: Available
LinuxLinux: Available
AndroidAndroid: Unavailable
iOSiOS: Unavailable

Choose it when

Choose Zen for a Firefox foundation with a modern vertical-tab and workspace workflow, especially if Arc-like organization without Chromium is attractive.

Avoid it when

Avoid it for conservative enterprise deployment, mobile coverage, or workflows that require a long-established release cadence.

Quick answers

Read straight off the verified record - every one of these is expanded with its source below.

Which platforms does Zen Browser run on?: Documented on macOS, Windows, and Linux. Not available on Android and iOS.
Can I install Chrome extensions?: No - the Chrome Web Store is not supported.
Does it block trackers out of the box?: Yes - tracker or ad blocking is on by default. Firefox-derived tracking protection is enabled by default.
Does it have built-in AI features?: No AI capability in this record is documented as built in.
Is it open source?: Open source Firefox-derived project
Is it still being developed?: Active - Actively developed and distributed as a beta with a fast-moving release process; verify current build support.

What Zen Browser does

Open any row for the wording and the source behind it

Privacy and tracking

2 built in · 1 not available · 1 undocumented

Blocks trackers by defaultBlocks trackers by default: Built in
Firefox-derived tracking protection is enabled by default.
Anti-fingerprintingAnti-fingerprinting: Built in
Firefox-derived protections are available, with Zen-specific scope not independently claimed.
Telemetry postureTelemetry posture: Unknown
Zen's current telemetry posture should be checked against its project policy before deployment.
Built-in VPN or proxyBuilt-in VPN or proxy: Unavailable
No browser VPN is included.
Private windowsPrivate windows follow Firefox behavior and do not provide anonymity.
Private windows follow Firefox behavior and do not provide anonymity.
Default search engineGoogle

Extensions and blocking

4 built in · 1 not available

Chrome Web StoreChrome Web Store: Unsupported
Firefox Add-onsFirefox Add-ons: Supported
Native content blockingNative content blocking: Built in
Firefox-derived tracking protection is native.
Manifest V3Manifest V3: Built in
Firefox-derived Manifest V3 support is available with compatibility differences.
Manifest V2Manifest V2: Built in
Zen follows Firefox WebExtensions behavior.
Known limitationsFirefox Add-ons are the supported ecosystem; Chrome Web Store installation is not the supported path.
Firefox Add-ons are the supported ecosystem; Chrome Web Store installation is not the supported path.

Workflow

11 built in

Vertical tabsVertical tabs: Built in
Vertical tabs are central to Zen's compact layout.
Tab treesTab trees: Built in
Zen's tab organization supports nested or grouped workflows.
Workspaces or spacesWorkspaces or spaces: Built in
Workspaces are a documented Zen workflow feature.
ProfilesProfiles: Built in
Firefox profiles remain available for separated contexts.
Split viewSplit view: Built in
Zen documents a Split View that shows up to four tabs side by side.
SidebarSidebar: Built in
The compact sidebar hosts tabs and controls.
Reader modeReader mode: Built in
Firefox Reader View is available.
Command paletteCommand palette: Built in
Zen ships a native command bar with global actions.
Sync across devicesSync across devices: Built in
Firefox Sync compatibility is available.
TranslationTranslation: Built in
Firefox-derived translation is available for supported languages.
Progressive web appsProgressive web apps: Built in
Progressive web apps are supported by the Chromium install flow.

AI features

9 not available

Built-in assistantBuilt-in assistant: Unavailable
Page summarisationPage summarisation: Unavailable
Acts on pages for youActs on pages for you: Unavailable
AI answer engineAI answer engine: Unavailable
Works across open tabsWorks across open tabs: Unavailable
Text or image generationText or image generation: Unavailable
Choice of modelChoice of model: Unavailable
Retention or training controlsRetention or training controls: Unavailable
Voice or image inputVoice or image input: Unavailable

On a phone

10 undocumented

Undocumented is not the same as absent - it means the publisher does not state it.

Extensions on mobileExtensions on mobile: Unknown
Extension support on mobile is not documented.
Can be the phone defaultCan be the phone default: Unknown
Default-browser capability is not documented.
Biometric lockBiometric lock: Unknown
Biometric locking is not documented.
Offline readingOffline reading: Unknown
Offline reading is not documented.
Desktop-site modeDesktop-site mode: Unknown
Desktop-site mode is not documented.
Download managerDownload manager: Unknown
A built-in download manager is not documented.
Background playbackBackground playback: Unknown
Background or picture-in-picture playback is not documented.
Web pushWeb push: Unknown
Web push support is not documented.
Data saverData saver: Unknown
Address-bar placementAddress-bar placement: Unknown
Address-bar placement is not documented.

Under the hood

Rendering engine: Gecko
JavaScript engine: SpiderMonkey
Upstream project: Mozilla Firefox
Release channel: rolling
Code and licence: Open source Firefox-derived project
Install method: Official desktop download.
Hardware support: Desktop architecture support follows the current download page.

Source repository

Active. Actively developed and distributed as a beta with a fast-moving release process; verify current build support.

Editorial view

Zen is the Arc idea rebuilt on Firefox, by a community, in the open, and still labelled beta by its own site. The sidebar is the default interface rather than an option, on Gecko and SpiderMonkey with Mozilla Firefox as the upstream. Official builds cover macOS, Windows, and Linux. There is no mobile app, and the release cadence is rolling and fast.

The layout

Compact vertical tabs as the default chrome, not a setting
Workspaces and nested tab folders
Split view up to four panes
A native command bar, plus the Firefox sidebar underneath

Why Gecko matters here

The pitch in one line: Arc-style organisation without Chromium. Firefox Add-ons install normally, Manifest V2 and V3 both work under Mozilla's policy, uBlock Origin runs at full strength, and Firefox Sync, Reader View, and translation carry over. For someone who wants engine diversity and a modern layout in the same browser, Zen is currently the clearest answer in this directory, and its Linux support is first-class where Arc's never existed.

Privacy, inherited

Firefox's Enhanced Tracking Protection and fingerprinting controls are enabled, private windows behave like Firefox's, Google is the default engine, and there is no VPN. The project says it strips telemetry, but this profile records the posture as unknown rather than repeating a claim it has not verified. Check the project's documentation if that field decides anything for you.

The honest cost

Project maturity. Beta means beta: a fast-moving community codebase where features land, move, and occasionally break, tracking each Firefox release closely. That is fine for an enthusiast's daily driver and a poor fit for a conservative fleet, a machine you rarely update, or anyone who wants this year's browser to behave like last year's.

The verdict

Choose Zen if vertical tabs, workspaces, and a keyboard-driven sidebar describe the workflow you want and you would rather have it on Gecko than Chromium. Avoid it for mobile coverage, enterprise stability, or set-and-forget use. Before you commit a long-lived profile, run it beside your current browser for a couple of weeks, because rolling releases reward people who keep a fallback. Your Firefox profile data imports cleanly, which lowers the cost of the experiment to roughly zero.

Where these facts come from

Every capability above is read from a primary source and dated. 1 of 30 fields stay recorded as unknown rather than assumed.

Zen Browser official site
Product, release channel, and platform scope.
Verified Sep 2026

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Head to head

Reviewed comparisons featuring Zen Browser

Arc vs Zen
Choose Arc for a polished Chromium sidebar-and-spaces model; choose Zen for a Firefox-based alternative with vertical navigation and a fast-moving community release cadence.
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