SigmaOS alternatives.

Arc is The Browser Company’s Chromium browser for Mac and Windows that put tabs down the side, with spaces, folders and Split View. It has had no new features since May 2025; it still gets security fixes, and its makers point people to Dia.

Keeps: tabs down the side, spaces, Split View, AI chat about pages, Chrome extensions and a free price. Misses: an ad blocker.

Pick it if you use it today and want its sidebar, spaces and Split View exactly as they are. The catch: No new features since May 2025, only security updates.

Vivaldi is a Chromium browser with a setting for nearly everything, mail, calendar and feeds built in, a free Proton VPN and no AI by design, on every desktop and phone.

Keeps: tabs down the side (as a setting), spaces, Split View, Chrome extensions, an ad blocker and a free price. Misses: AI chat about pages.

Pick it if you want mail, calendar, feeds, notes and a VPN in the browser. The catch: No AI assistant or agent, by design.

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.

Keeps: tabs down the side, spaces, Split View and a free price. Misses: AI chat about pages, Chrome extensions and an ad blocker.

Pick it if you want Arc’s layout, free and open source. The catch: Releases are still labeled beta.

Aside is an AI agent browser from a Y Combinator startup, on Chromium, for Mac and Windows. Its agent does multi-step work in the sites you are signed in to, on Aside’s own models or your ChatGPT or Claude plan.

Keeps: tabs down the side, spaces, Split View, AI chat about pages, Chrome extensions, an ad blocker and a free price.

Pick it if you want an agent for multi-step work across your signed-in sites, on Mac or Windows. The catch: The free plan has 500 AI credits a month; more is Pro at $20 or Max at $200.

Orion is Kagi’s browser for Mac, iPhone and iPad, on WebKit, the engine Safari uses, that also runs many Chrome and Firefox extensions. It has no telemetry and blocks ads by default.

Keeps: tabs down the side (as a setting), spaces, AI chat about pages, Chrome extensions, an ad blocker and a free price. Misses: Split View.

Pick it if you want Safari’s engine with Chrome and Firefox extensions, on Mac and iPhone. The catch: Apple only: the Windows and Linux versions stopped on October 2, 2026.

Opera One is Opera’s free Chromium browser on every desktop and phone, with a free browser VPN, an ad blocker, messengers in the sidebar and Opera AI. Its agents are in a separate browser, Opera Neon.

Keeps: tabs down the side (as a setting), spaces, Split View, AI chat about pages, Chrome extensions, an ad blocker and a free price.

Pick it if you want a free browser VPN and an ad blocker built in. The catch: Opera AI only chats and sums up; agents need Opera Neon at $19.90 a month.

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.

Keeps: tabs down the side (as a setting), spaces, Split View, AI chat about pages, Chrome extensions, an ad blocker and a free price.

Pick it if you want the current browser from Arc’s makers, with Arc import and tabs down the side as a setting. The catch: AI costs $20 or $100 a month for new users; the free plan has none after a 14-day trial.