YabZen vs Firefox
Zen is a free, open-source browser built on Firefox that brings Arc’s layout, tabs down the side with spaces, folders and Split View, to Mac, Windows and Linux.
Firefox is Mozilla’s open-source browser on its own engine, Gecko, on every desktop and phone. Its AI is optional: a Smart Window beta and a sidebar chatbot, all behind one switch.
Zen is Firefox underneath, with Arc’s layout on top: tabs down the side, spaces and folders by default. It switches Firefox’s AI off and is still labeled beta.
The short answer
- if you want Arc’s layout, free and open source
- if you prefer Firefox’s engine and its add-ons
- if you want no AI in your browser at all
- if you want an open-source browser that isn’t Chromium
- if you want AI off by default, or gone with one switch
- if you want a free browser VPN, where it is offered
- if you miss Arc and want spaces, pins and folders kept, on a Mac
- if you already pay for Claude or ChatGPT and want it to work in your signed-in tabs
- if you want Claude Code, Codex or Cursor to drive a real browser over MCP
At a glance
Zen and Firefox, with Yab beside them for a Mac.
| What | Zen Browser | Firefox | Yab |
|---|---|---|---|
| Made by | Zen Browser team (open-source community project) | Mozilla | Serafim Korablev |
| Status | Updated | Updated | Updated |
| Runs on | Mac, Windows and Linux | Mac, Windows, Linux, iPhone and Android | Mac |
| Phone app | None; Zen says it has no plans for a mobile version | iPhone, iPad and Android; syncs tabs, bookmarks, passwords and history | Not yet |
| Price | Free and open source | Free; its built-in VPN is free up to 50 GB a month | Free; its AI runs on your own Claude or ChatGPT plan |
| AI | No AI | Chat about pages, on its own AI or yours | An agent that works in pages, on your Claude or ChatGPT plan |
| Driven by outside agents | No | MCP | MCP and a command line |
| Engine | Gecko | Gecko | WebKit |
| Tabs down the side | Yes | A setting | Yes |
| Spaces | Yes | No | Yes |
| Split View | Yes | Yes | Yes |
| Extensions | Firefox add-ons | Firefox add-ons | Chrome Web Store |
| Ad blocker | No | No | Built in |
| Open source | Yes | Yes | No |
Checked October 9, 2026 on each maker’s own pages, linked under Sources. Prices are per month, in US dollars.
Where they differ
What separates them, area by area. Where one plainly has more, it says who; where it comes down to taste, it says so.
AIFirefox leads
Firefox has AI built in; Zen has less of it. Zen has no AI: Firefox’s AI features are switched off by default. Firefox’s Smart Window beta chats with tabs you share and groups them, and a sidebar chatbot can use Claude, ChatGPT, Gemini, Le Chat or Copilot; it can’t click or fill forms, and one switch turns all AI off.
Agents like Claude Code and CodexFirefox leads
Zen has no MCP server or command line for outside agents. Firefox can be driven over MCP, through Mozilla’s Firefox DevTools MCP, which starts its own Firefox.
Tabs and windowsZen leads
Zen has tabs down the side, spaces, Split View, folders in the sidebar and tabs that sleep. Firefox has tabs down the side as a setting, Split View, folders in the sidebar and tabs that sleep.
PriceFirefox leads
Zen: Free and open source. Firefox: Free; its built-in VPN is free up to 50 GB a month.
Where it runsFirefox leads
Zen runs on Mac, Windows and Linux. Firefox runs on Mac, Windows, Linux, iPhone and Android. On a Mac, Zen needs macOS 10.15 or later and Firefox needs macOS 10.15 or later. Zen has no phone app: Zen says it has no plans for a mobile version. On the phone, Firefox: iPhone, iPad and Android; syncs tabs, bookmarks, passwords and history.
Engine and extensionsa matter of taste
Both are built on Gecko, Firefox’s engine. Both take extensions from Firefox’s add-ons.
PrivacyFirefox leads
Zen has open code. Zen sends no telemetry or crash reports, by its privacy policy; optional sync keeps encrypted data on Mozilla’s servers. Firefox has a VPN and open code. Smart Window sends prompts and what you share through Mozilla’s servers to partner models; Mozilla says it keeps no chat logs without permission and doesn’t train on them.
What their pages don’t lead with
Real limits, from the makers’ own words and our own use.
Zen Browser
- Releases are still labeled beta
- No phone app, and none planned
- Firefox add-ons only, not the Chrome Web Store
- No ad blocker of its own beyond Firefox’s tracking protection
Firefox
- Its Smart Window AI is a beta in the US, Canada and France and needs a Mozilla account
- Its AI can’t click, fill forms or buy for you
- The free VPN covers the browser only, up to 50 GB a month, in a few countries
- Firefox add-ons only, not the Chrome Web Store
Yab, honestly
- Mac only: macOS 15.4 or later, no Windows, iPhone or Android
- New: first released in September 2026
- Its AI needs a Claude or ChatGPT plan; ChatGPT’s free plan may work with low limits
- WebKit, as in Safari: a site tested only in Chrome can misbehave
- Closed source
What changed lately
- September 16, 2026Firefox: Smart Window beta expanded from the US and Canada to France
- September 5, 2026Zen: Spaces, folders and tabs sync between devices with a Mozilla account (1.22b)
- March 24, 2026Firefox: Firefox 149 added split view and a free built-in VPN
- February 28, 2026Zen: Live folders for GitHub issues, pull requests and RSS (1.19b)
- February 24, 2026Firefox: Firefox 148 added AI Controls with a switch that blocks all AI features
- August 27, 2025Zen: Tab folders added (1.15b)
Questions
Is Zen Browser free?
Yes. Free and open source.
Is Firefox free?
Yes. Free; its built-in VPN is free up to 50 GB a month.
Which has an AI agent, Zen or Firefox?
Neither has an agent that does tasks in your pages. Zen has no AI: Firefox’s AI features are switched off by default. Firefox’s Smart Window beta chats with tabs you share and groups them, and a sidebar chatbot can use Claude, ChatGPT, Gemini, Le Chat or Copilot; it can’t click or fill forms, and one switch turns all AI off.
Do Zen and Firefox run on Windows?
Yes, both. Zen runs on Mac, Windows and Linux; Firefox on Mac, Windows, Linux, iPhone and Android.
Do Zen and Firefox have phone apps?
Firefox does. Zen has no phone app: Zen says it has no plans for a mobile version. On the phone, Firefox: iPhone, iPad and Android; syncs tabs, bookmarks, passwords and history.
Is there a third option on a Mac?
Yab, Yet Another Browser, is free for the Mac: tabs down the side with spaces, folders and Split View, as in Zen; an agent that works in your signed-in tabs, on the Claude or ChatGPT plan you already pay for. Claude Code, Codex and any MCP client can drive it too. It runs on WebKit, the engine Safari uses, and takes Chrome extensions. It is Mac only, and new.
More comparisons
- Zen home page
- Zen download page (macOS universal, Windows, Linux; beta)
- Zen 1.23.2b release (macOS universal dmg; Info.plist minimum 10.15)
- Zen 1.23.1b release (Firefox 157.0.1)
- Zen license (MPL-2.0)
- Zen AI preferences (all off)
- Zen welcome flow (Firefox import wizard)
- Firefox import from another browser
- Zen 1.15b release (folders)
- Zen 1.19b release (live folders)
- Zen 1.22b release (sync)
- Zen 1.12.9b release (tab unloader uses Firefox tab discarding)
- Zen FAQ (no mobile plans, donations)
- Zen Workspaces
- Zen Split View
- Zen Extensions (addons.mozilla.org)
- Zen Privacy and Security (Firefox password manager, tracking protection)
- Zen privacy policy
- Firefox 157 system requirements
- Mozilla blog: Smart Window
- Mozilla Support: get started with Smart Window
- Mozilla Support: model choices in Smart Window
- Smart Window privacy notice
- Firefox.com: Smart Window
- Mozilla blog: window types (2026-09-24)
- Mozilla blog: AI on your terms (AI controls)
- Firefox 148 release notes
- Firefox 149 release notes (split view, VPN)
- Mozilla blog: free built-in VPN
- Firefox 136 release notes (vertical tabs)
- Firefox 138 release notes (tab groups)
- Bugzilla 1730066: tab unloading enabled on macOS (Firefox 95)
- Firefox system requirements
- Firefox ESR 115 release notes (import sources)
- Firefox DevTools MCP (Mozilla)
- Firefox.com: Firefox browser sync
- Firefox on the App Store (iPhone and iPad)
- Firefox on Google Play
- Mozilla Support: Sync Firefox data
- Yab Manual: Bringing in from another browser
- Yab Manual: Connecting Claude or ChatGPT
- Yab Manual: Extensions
- Yab Manual: Yab’s tools over MCP
- Yab Manual: Privacy
Yab, Yet Another Browser.
Free for the Mac. Arc’s sidebar, your own Claude or ChatGPT as the agent, Chrome extensions on WebKit.