Dia vs Firefox

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

Dia is the AI browser The Browser Company builds now instead of Arc. It is Chromium-based, for Macs with Apple silicon and, since October 2026, Windows, and its AI chats with your tabs and the tools you connect.

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

Pick Dia

if you want the current browser from Arc’s makers, with Arc import and tabs down the side as a setting
if you want AI that chats across your tabs, Gmail, Slack and Notion, and will pay for it
if you want a free browser with an ad blocker and no AI

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 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

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

Dia vs Firefox
What	Dia	Firefox	Yab
Made by	The Browser Company (Atlassian)	Mozilla	Serafim Korablev
Status	Updated	Updated	Updated
Runs on	Mac and Windows	Mac, Windows, Linux, iPhone and Android	Mac
Phone app	None	iPhone, iPad and Android; syncs tabs, bookmarks, passwords and history	Not yet
Price	Browser free; AI on Better Answers $20/month or Better Days $100/month	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	Chat about 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	Yes	No	Yes
Split View	Yes	Yes	Yes
Extensions	Chrome Web Store	Firefox add-ons	Chrome Web Store
Ad blocker	Built in	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.

AIa matter of taste

Both have AI to ask about pages, and neither does the clicking for you. Dia chats with your tabs and the tools you connect, like Gmail, Slack and Notion, and drafts mail and invites; there is no documented agent that works through sites. 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

Dia 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 windowsDia leads

Dia has tabs down the side as a setting, 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

Dia: Browser free; AI on Better Answers $20/month or Better Days $100/month. Firefox: Free; its built-in VPN is free up to 50 GB a month.

Where it runsFirefox leads

Dia runs on Mac and Windows. Firefox runs on Mac, Windows, Linux, iPhone and Android. On a Mac, Dia needs macOS 14 or later and Firefox needs macOS 10.15 or later. Dia has no phone app. On the phone, Firefox: iPhone, iPad and Android; syncs tabs, bookmarks, passwords and history.

Engine and extensionsa matter of taste

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

PrivacyFirefox leads

Dia has an ad blocker built in. Dia’s chat goes through its servers to Anthropic, OpenAI and Google; chats and history stay on your Mac, and content sharing is on by default, kept 30 days. 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.

Dia

AI costs $20 or $100 a month for new users; the free plan has none after a 14-day trial
On a Mac it needs Apple silicon and macOS 14 or later
Its AI chats and drafts, but there is no documented agent that works through sites
No MCP server or command line for outside agents

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

October 6, 2026Dia: Dia 1.0 for Windows released
September 16, 2026Firefox: Smart Window beta expanded from the US and Canada to France
August 17, 2026Dia: Paid AI plans started rolling out to new Mac users
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, 2025Dia: Atlassian completed its acquisition of The Browser Company

Questions

Is Dia free?

The browser is; its AI isn’t. Browser free; AI on Better Answers $20/month or Better Days $100/month.

Is Firefox free?

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

Which has an AI agent, Dia or Firefox?

Neither has an agent that does tasks in your pages. Dia chats with your tabs and the tools you connect, like Gmail, Slack and Notion, and drafts mail and invites; there is no documented agent that works through sites. 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 Dia and Firefox run on Windows?

Yes, both. Dia runs on Mac and Windows; Firefox on Mac, Windows, Linux, iPhone and Android.

Do Dia and Firefox have phone apps?

Firefox does. Dia has no phone app. 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 Dia; 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

Comet vs Dia Atlas vs Dia Opera Neon vs Dia Aside vs Dia Dia vs Chrome Dia vs Safari Dia vs Edge Dia alternatives Yab vs Dia Firefox vs Chrome Firefox vs Safari Firefox vs Edge Brave vs Firefox Opera vs Firefox Arc vs Firefox Comet vs Firefox Firefox alternatives Yab vs Firefox

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.

it’s freeMove from Dia Download