YabZen 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.
ChatGPT Atlas was OpenAI’s Chromium browser for the Mac, with ChatGPT beside every page and an agent mode. OpenAI shut it down on August 9, 2026, and points people to the ChatGPT desktop app and its Chrome extension.
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
- OpenAI shut Atlas down on August 9, 2026: it may not open, runs no agent tasks and gets no security updates
- 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
At a glance
Zen and Atlas, with Yab beside them for a Mac.
| What | Zen Browser | ChatGPT Atlas | Yab |
|---|---|---|---|
| Made by | Zen Browser team (open-source community project) | OpenAI | Serafim Korablev |
| Status | Updated | Shut down August 9, 2026 | Updated |
| Runs on | Mac, Windows and Linux | Mac | Mac |
| Phone app | None; Zen says it has no plans for a mobile version | None; Atlas was Mac only and shut down on Aug 9, 2026 | Not yet |
| Price | Free and open source | Shut down; it was free, with agent mode on paid ChatGPT plans | Free; its AI runs on your own Claude or ChatGPT plan |
| AI | No AI | An agent that works in pages, on its own AI service | An agent that works in pages, on your Claude or ChatGPT plan |
| Driven by outside agents | No | No | MCP and a command line |
| Engine | Gecko | Chromium | WebKit |
| Tabs down the side | Yes | A setting | Yes |
| Spaces | Yes | Not stated | Yes |
| Split View | Yes | Not stated | Yes |
| Extensions | Firefox add-ons | Chrome Web Store | Chrome Web Store |
| Ad blocker | No | Not stated | Built in |
| Open source | Yes | No | 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.
AIAtlas leads
Only Atlas has an agent that clicks, types and finishes tasks in your pages. Zen has no AI: Firefox’s AI features are switched off by default. Atlas put ChatGPT beside every page, with optional browser memories and, on paid plans, an agent mode; it no longer works.
Tabs and windowsZen leads
Zen has tabs down the side, spaces, Split View, folders in the sidebar and tabs that sleep. Atlas has tabs down the side as a setting and folders in the sidebar.
PriceZen leads
Zen: Free and open source. Atlas: Shut down; it was free, with agent mode on paid ChatGPT plans.
Where it runsZen leads
Zen runs on Mac, Windows and Linux. Atlas runs on Mac. On a Mac, Zen needs macOS 10.15 or later and Atlas needs macOS 14.2 or later. Zen has no phone app: Zen says it has no plans for a mobile version. Atlas has no phone app: Atlas was Mac only and shut down on Aug 9, 2026.
Engine and extensionsa matter of taste
Zen is built on Gecko, Firefox’s engine; Atlas on Chromium, as Chrome is. Zen takes extensions from Firefox’s add-ons, Atlas from the Chrome Web Store.
PrivacyZen 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. Atlas has no ad blocker of its own. Atlas summed up pages for browser memories and deleted the originals; training on browsing was off by default.
UpdatesZen leads
Zen is updated as usual. Atlas: OpenAI shut Atlas down on August 9, 2026: it may not open, runs no agent tasks and gets no security updates.
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
ChatGPT Atlas
- Shut down on August 9, 2026, with no more security updates
- Was Mac only, on Apple silicon
- Bookmarks, tabs and history had to be exported by hand
- Agent mode needed a paid ChatGPT plan
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 5, 2026Zen: Spaces, folders and tabs sync between devices with a Mozilla account (1.22b)
- August 9, 2026Atlas: Atlas shut down
- July 9, 2026Atlas: OpenAI said it will sunset Atlas for the new ChatGPT desktop app
- February 28, 2026Zen: Live folders for GitHub issues, pull requests and RSS (1.19b)
- October 21, 2025Atlas: Launched for macOS
- August 27, 2025Zen: Tab folders added (1.15b)
Questions
Is Zen Browser free?
Yes. Free and open source.
Is ChatGPT Atlas free?
It no longer works. Shut down; it was free, with agent mode on paid ChatGPT plans.
Which has an AI agent, Zen or Atlas?
Atlas. Zen has no AI: Firefox’s AI features are switched off by default. Atlas put ChatGPT beside every page, with optional browser memories and, on paid plans, an agent mode; it no longer works.
Which runs on Windows, Zen or Atlas?
Zen does. Atlas runs on Mac.
Do Zen and Atlas have phone apps?
Zen has no phone app: Zen says it has no plans for a mobile version. Atlas has no phone app: Atlas was Mac only and shut down on Aug 9, 2026.
Is ChatGPT Atlas shut down?
OpenAI shut Atlas down on August 9, 2026: it may not open, runs no agent tasks and gets no security updates.
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 in your signed-in tabs like Atlas’s, 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
- OpenAI help: Evolving Atlas into ChatGPT (retirement notice)
- OpenAI help: Atlas release notes (vertical tabs, tab groups, imports, profiles)
- OpenAI help: Getting started with Atlas (macOS 14.2, Apple silicon)
- OpenAI help: Setting up Atlas (imports, password manager)
- OpenAI help: Atlas data controls and privacy
- 9to5Mac: OpenAI is discontinuing Atlas (Jul 9, 2026, James Sun quote)
- 9to5Mac: what happens when Atlas shuts down (Aug 4, 2026)
- TechRepublic: Atlas shuts down Aug 9
- TechCrunch: Atlas launch (Oct 21, 2025)
- Wikipedia: ChatGPT Atlas (Chromium, timeline)
- OpenAI Help: ChatGPT Atlas retirement
- OpenAI Help: ChatGPT release notes (Jul 9, 2026 deprecation entry)
- TechRadar: Atlas for macOS, Windows, iOS and Android ’coming soon’ (Oct 2025)
- 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.