Atlas vs Firefox

We make Yab, the third column.facts checked Oct 9 ↓

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.

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.

The short answer

AtlasShut down

OpenAI shut Atlas down on August 9, 2026: it may not open, runs no agent tasks and gets no security updates

Pick Firefox

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

Or Yabours

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

Atlas and Firefox, with Yab beside them for a Mac.

Atlas vs Firefox
What	ChatGPT Atlas	Firefox	Yab
Made by	OpenAI	Mozilla	Serafim Korablev
Status	Shut down August 9, 2026	Updated	Updated
Runs on	Mac	Mac, Windows, Linux, iPhone and Android	Mac
Phone app	None; Atlas was Mac only and shut down on Aug 9, 2026	iPhone, iPad and Android; syncs tabs, bookmarks, passwords and history	Not yet
Price	Shut down; it was free, with agent mode on paid ChatGPT plans	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	An agent that works in pages, on its own AI service	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	Chromium	Gecko	WebKit
Tabs down the side	A setting	A setting	Yes
Spaces	Not stated	No	Yes
Split View	Not stated	Yes	Yes
Extensions	Chrome Web Store	Firefox add-ons	Chrome Web Store
Ad blocker	Not stated	No	Built in
Open source	No	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.

AIAtlas leads

Only Atlas has an agent that clicks, types and finishes tasks in your pages. Atlas put ChatGPT beside every page, with optional browser memories and, on paid plans, an agent mode; it no longer works. 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

Atlas 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 windowsFirefox leads

Atlas has tabs down the side as a setting and folders in the sidebar. Firefox has tabs down the side as a setting, Split View, folders in the sidebar and tabs that sleep.

PriceFirefox leads

Atlas: Shut down; it was free, with agent mode on paid ChatGPT plans. Firefox: Free; its built-in VPN is free up to 50 GB a month.

Where it runsFirefox leads

Atlas runs on Mac. Firefox runs on Mac, Windows, Linux, iPhone and Android. On a Mac, Atlas needs macOS 14.2 or later and Firefox needs macOS 10.15 or later. Atlas has no phone app: Atlas was Mac only and shut down on Aug 9, 2026. On the phone, Firefox: iPhone, iPad and Android; syncs tabs, bookmarks, passwords and history.

Engine and extensionsa matter of taste

Atlas is built on Chromium, as Chrome is; Firefox on Gecko, Firefox’s engine. Atlas takes extensions from the Chrome Web Store, Firefox from Firefox’s add-ons.

PrivacyFirefox leads

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. 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.

UpdatesFirefox leads

Atlas: OpenAI shut Atlas down on August 9, 2026: it may not open, runs no agent tasks and gets no security updates. Firefox is updated as usual.

What their pages don’t lead with

Real limits, from the makers’ own words and our own use.

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

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
August 9, 2026Atlas: Atlas shut down
July 9, 2026Atlas: OpenAI said it will sunset Atlas for the new ChatGPT desktop app
March 24, 2026Firefox: Firefox 149 added split view and a free built-in VPN
February 24, 2026Firefox: Firefox 148 added AI Controls with a switch that blocks all AI features
October 21, 2025Atlas: Launched for macOS

Questions

Is ChatGPT Atlas free?

It no longer works. Shut down; it was free, with agent mode on paid ChatGPT plans.

Is Firefox free?

Yes. Free; its built-in VPN is free up to 50 GB a month.

Which has an AI agent, Atlas or Firefox?

Atlas. Atlas put ChatGPT beside every page, with optional browser memories and, on paid plans, an agent mode; it no longer works. 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.

Which runs on Windows, Atlas or Firefox?

Firefox does. Atlas runs on Mac.

Do Atlas and Firefox have phone apps?

Firefox does. Atlas has no phone app: Atlas was Mac only and shut down on Aug 9, 2026. On the phone, Firefox: iPhone, iPad and Android; syncs tabs, bookmarks, passwords and history.

Can I move from Firefox to Atlas?

Yes: Atlas’s own help says it brings in from Firefox.

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 as in Arc, with spaces, folders and Split View; 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.

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Sources, read October 9, 2026. Something out of date? Write to hello@serafimlabs.io and we fix it.

Yab, Yet Another Browser.

Free for the Mac. Arc’s sidebar, your own Claude or ChatGPT as the agent, Chrome extensions on WebKit.

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