Zen Browser is a free, open-source Firefox fork that picked up the interface ideas Arc left behind when The Browser Company stopped developing it: a vertical tab sidebar, Workspaces that split tabs by project, Split View tiling, and a Glance popup that previews a link without leaving the page. As a productivity shell over Gecko it works, and the project is popular — 44.6k GitHub stars, 241 contributors, 190 releases since the first stable build on 11 July 2024. As a privacy browser it doesn’t hold up: the default search engine is Google with live suggestions, there’s no blocker beyond what Firefox already ships, and the network connections a fresh install makes on its own have been documented in detail by the project’s own contributors and left in place by its maintainers.

Privacy Defaults

Zen’s marketing line is “We care about your experience, not your data,” and the privacy policy opens with “We don’t sell data - We don’t collect data - We don’t track you.” What ships is closer to stock Firefox with the telemetry switches flipped and the productivity UI on top.

Search is the first thing a privacy-focused default would change, and Zen doesn’t. Google is the default engine, and address-bar suggestions are on, which means keystrokes go to Google as they are typed — a maintainer confirmed this in the project’s own discussion thread rather than disputing it. There is no built-in ad or tracker blocker. Protection is whatever Firefox’s Enhanced Tracking Protection provides in its Standard mode, the same as an unmodified Firefox install. HTTPS-Only Mode exists but is not stated as on by default, and DNS-over-HTTPS appears in Zen’s documentation as something users can enable, not as a shipped setting.

The bigger problem is what a fresh install does before you open a single tab. With no extensions and no browsing, the browser reaches out to Mozilla’s telemetry endpoint, its location service, its remote-settings service, its Merino suggestion service, and its push-notification service, plus Google, Akamai, and GitHub infrastructure — the last group traced by a contributor’s packet capture to default pinned shortcut tabs pointing at Google Calendar, Trello, WhatsApp Web, Notion, YouTube, GitHub, and Slack. The connectivity check, the geolocation lookup, and the push-service registration all fire on startup and are not opt-in. Zen’s privacy policy discloses this in outline — startup connections happen, and they “can be disabled through the browser flags (about:config)” — meaning the only way off is editing hidden preferences, not a setup prompt or a settings toggle. The same policy states plainly: “We try to disable all telemetry data collection in Zen. But, we may have missed some.”

When contributors asked for those defaults to be stripped, a maintainer’s answer was “Why exactly? The connections fail anyways and no data is stored.” The README tagline was subsequently softened from an unqualified “privacy-focused” framing to “a balance of speed, privacy and productivity.” The defaults themselves were not changed.

Anti-Fingerprinting

There is nothing here beyond Firefox’s baseline. Resist Fingerprinting is not on, and Zen adds no canvas or WebGL randomization of its own, so the surface a script can read — canvas output, WebGL parameters, fonts, screen metrics, audio characteristics — is whatever Firefox exposes.

Testing bears that out. A Cover Your Tracks run returned a uniquely identifying result, and a careful side-by-side check with both browsers configured identically (Enhanced Tracking Protection on Strict, the same ad-blocking extension and filter lists on each) found Zen and vanilla Firefox scoring the same: both unique, both conveying at least 17.88 bits of identifying information, with an identical user-agent string. The issue was closed as not planned. Zen neither improves nor worsens fingerprinting exposure relative to the browser it forks — which is the point. A fork marketed on privacy that adds a redesigned sidebar and no fingerprinting defense at all is, on this axis, the browser it started from.

Transparency & Audits

The code side is solid. The full source tree is public under MPL-2.0 and buildable with the standard Mozilla tooling, the contributor list is long and real, and the team is named individually on the about page with each person’s area of responsibility. That’s genuine openness, and it’s the reason the network behavior above is documented at all — outside contributors could run packet captures and file what they found.

What’s missing is everything past the repository. No independent third-party security audit has been conducted or published. The entire security policy is a two-line SECURITY.md pointing at GitHub’s vulnerability-report form, with no named security contact and no bug-bounty program. Governance is one primary developer, Mauro V., listed as creator and main developer, with roughly a dozen volunteers covering specific areas; the project’s own FAQ calls the team “currently very small.” That bus factor is common among independent forks, but it usually comes paired with unusually detailed disclosure documentation, and here it doesn’t.

Two specific incidents shape the score. An early version shipped with remote debugging enabled by default and the connection-confirmation prompt disabled, which put a remote-code-execution surface in front of anyone on the same network. That one was reported, fixed in a merged pull request, and acknowledged by the maintainer roughly seven months before the privacy discussion above; the fix held, and it reads as a mistake handled properly. The privacy-connections episode reads differently. The original bug report was closed without the technical explanation that had been asked for, the follow-up discussion ran to 15 participants before being locked as too heated, and the outcome was a marketing-language edit rather than a defaults change. The gap between “we don’t track you” and what the browser does on first launch is documented, acknowledged by the people who could close it, and still open.

Usability & Compatibility

Anything on addons.mozilla.org installs and runs, since Zen is Firefox underneath and uses the same extension store. Firefox themes are the exception — Zen has its own CSS-based theming system, Zen Mods, which is architecturally separate from extensions. Security patches arrive fast: the project rebases onto each new Firefox release within 0 to 72 hours and tests Release Candidate builds about a week ahead on a separate Twilight channel. On the feature side, Workspaces, Compact Mode, Glance, Split View, and the tab folders added in August 2025 are the reason people install it.

The hard limit is DRM. Zen has no Widevine license, and per its own FAQ that means Netflix, Spotify, Disney+, HBO Max, Amazon Prime Video, Apple Music, and Google Play Movies & TV do not play at all on Windows or macOS. The project says it is pursuing a license from Google with no timeline attached. For anyone who wants one browser for everything, that’s disqualifying rather than inconvenient, and it’s the flaw reviewers outside this site have singled out too.

Beta status is the other caveat. More than two years after the first stable release the current build is versioned 1.22.2b, the download page carries a beta banner, and the user manual describes itself as incomplete and liable to go out of date as the browser changes. That is an accurate self-description of a fast-moving project, not a daily driver that has settled.

Cross-Platform & Sync

Official builds cover Windows, macOS, and Linux. There is no Android or iOS version, and the FAQ says there are no plans for one: the team cites limited time and resources, and argues that a vertical sidebar and Workspaces don’t translate to a phone screen. That’s a defensible design call, but it caps the browser at desktop.

Sync itself is the strongest thing in Zen’s privacy column. It runs on Firefox Sync through a Mozilla Account, so bookmarks, history, and passwords move between machines end-to-end encrypted, with Mozilla holding ciphertext — Zen’s privacy policy states the project cannot read any of it. The limitation is scope rather than security: with no mobile build, sync can only ever join desktops.

Pros and Cons

Fully open source under MPL-2.0 with the complete browser tree public and buildable, a large active community (44.6k stars, 241 contributors, 190 releases), and every team member named with their area of responsibility
Tracks upstream Firefox within 0-72 hours of each release, and tests Firefox Release Candidate builds about a week early on a separate Twilight channel, so security fixes land quickly
Full Firefox extension compatibility through addons.mozilla.org — anything in that catalog installs and runs normally
The productivity layer is the real draw: a vertical tab sidebar, Workspaces for separating tabs by project, Split View tiling, a Glance link-preview popup, Compact Mode that hides the sidebar, and nested tab folders added in August 2025
Firefox Sync through a Mozilla Account is end-to-end encrypted, so bookmarks, history, and passwords move between desktops with Mozilla holding only ciphertext
Zen's own privacy policy discloses the startup connections and admits the telemetry-stripping may be incomplete rather than claiming a clean slate

Google is the default search engine, and address-bar suggestions send keystrokes to Google as you type — confirmed by a maintainer and left unchanged
No built-in ad or tracker blocker: protection out of the box is stock Firefox Enhanced Tracking Protection in Standard mode, nothing more
A fresh install with no tabs and no extensions connects to Mozilla telemetry, location, remote-settings, suggestion, and push services plus Google, Akamai, and GitHub infrastructure, the latter traced to default pinned shortcut tabs; these can only be stopped by editing about:config flags
Confronted with that documented behavior, a maintainer declined to change the defaults ("Why exactly? The connections fail anyways and no data is stored"), the bug report was closed without the requested technical explanation, and the outcome was a softened README tagline rather than a fix
No fingerprinting resistance beyond Firefox's baseline — a controlled side-by-side test put Zen and vanilla Firefox at an identical unique result, at least 17.88 bits of identifying information with the same user-agent string
No independent security audit exists, and the security policy is a two-line file pointing at GitHub's report form with no named contact and no bug bounty
An early version shipped with remote debugging enabled by default and its confirmation prompt disabled, a remote-code-execution surface for anyone on the same network; fixed and acknowledged, but it shipped
No Widevine license means Netflix, Spotify, Disney+, HBO Max, Amazon Prime Video, Apple Music, and Google Play Movies & TV don't play at all on Windows or macOS, with no timeline for a fix
Desktop only — no Android or iOS build, and the team says it has no plans for one
Still officially beta more than two years after the first stable release, with documentation the project describes as incomplete

Our Rating

Privacy Defaults5.5/10
Google is the default search engine with live search suggestions sent as you type; no built-in ad or tracker blocker beyond stock Firefox Enhanced Tracking Protection; multiple unsolicited first-run connections to Mozilla and Google services that maintainers have declined to change
Anti-Fingerprinting4.5/10
No fingerprinting resistance beyond stock Firefox; independent testing shows an identical, uniquely-identifying fingerprint to vanilla Firefox
Transparency4.5/10
Fully open source with a large, active repository, but run by one primary developer and a small volunteer team; no independent security audit; a remote-debugging security flaw shipped enabled by default until fixed; documented privacy complaints about default network connections were closed by maintainers without a technical explanation
Usability & Compatibility6.5/10
Full Firefox extension compatibility and a fast Firefox-tracking update cycle, but no DRM support means mainstream streaming services don't work on Windows or macOS, and the browser is still officially in beta more than two years after its first release
Cross-Platform & Sync5.5/10
Windows, macOS, and Linux only; the team has stated there are no plans for a mobile version; Firefox Sync is end-to-end encrypted when used

Overall5.2/10

Weighted: Privacy Defaults 30% · Anti-Fingerprinting 25% · Transparency 20% · Usability & Compatibility 15% · Cross-Platform & Sync 10%

See our rating methodology →

Zen is a well-built productivity browser that markets itself on privacy it doesn’t deliver. The defaults that matter most in this rubric are the ones it inherits or chooses badly: Google search with live suggestions, no blocker, no fingerprinting defense, and a set of unsolicited first-run connections its own contributors documented and its maintainers decided to keep. The transparency score isn’t about the missing audit so much as the response to that report — closed without explanation, then answered with a tagline edit. Add a DRM gap that breaks every mainstream streaming service on Windows and macOS, a desktop-only footprint with no mobile plans, and permanent beta status, and this lands at the bottom of the browsers covered here. If the vertical-tab-and-Workspaces interface is what you want, Zen delivers that and the open source is real. If you came for the privacy claim on the homepage, the shipped defaults don’t back it, and you would need to harden it yourself through about:config before it’s meaningfully different from the Firefox it forks.

Affiliate Disclosure

Zen Browser has no affiliate program, and this review carries no tracked link — the “Visit Site” button points to Zen’s own download page and earns PrivacyPick.com nothing. The project funds itself through Patreon and Ko-fi donations and a handful of sponsors rather than ads or affiliate deals; our rating and what we write are unaffected either way.