Rio vs SigmaOS
Rio and SigmaOS are both Mac browsers with tabs in a sidebar and an Arc import. Rio is built on Chromium 158, so Chrome extensions run as they do in Chrome, and its import brings Arc's saved passwords in the same step. Rio is free and open source, with 8 releases out by build 1474 on November 12, 2026.
Side by side
| Rio | SigmaOS | |
|---|---|---|
| Engine | Chromium 158 | WebKit |
| Chrome extensions | Run as in Chrome, Manifest V3 and side panels included | Its own version of the Chromium extension API; "you might face compatibility issues" |
| Arc passwords | In the same step as the rest of the import | "Later": export a CSV from Arc and import it |
| Releases | 8 from its launch on November 10 to build 1474 on November 12, 2026 | Newest in its update feed: 1.19.0, February 4, 2025 |
| Price | Free, every feature | Free plan; Personal Pro $20 a month, Personal Max $30 a month |
Every SigmaOS cell comes from SigmaOS's own site, docs and update feed, listed at the end.
Where Rio is ahead
- Chrome extensions, as in Chrome. Rio is built on Chromium, the engine Chrome Web Store extensions are written for, and side panel extensions open next to the page. SigmaOS runs on WebKit with its own version of the Chromium extension API, and its own Arc guide warns of compatibility issues. See Side panel.
- Your whole Arc setup at once. Rio's import brings spaces with their names, icons and colors, profiles, pinned tabs, folders, favorites, Today tabs, history, saved passwords and sign-ins in one step. SigmaOS's guide lists saved passwords as later, through a CSV export. See Move from Arc to Rio.
- Shipping now. Rio updates itself and shipped 8 releases from its launch on November 10 to build 1474 on November 12, 2026. The newest release in SigmaOS's update feed is from February 4, 2025.
- Free, all of it. Every Rio feature is free. The Ask row opens ChatGPT, Claude or Grok, your pick, and tab tidying runs on Apple's on-device model at no cost. SigmaOS's paid plans are $20 and $30 a month.
- Open source. Rio's code is on GitHub under GPL-3.0, so anyone can read it, build it and keep it going.
Who Rio is for
People leaving Arc who want their Chrome extensions to keep working, their passwords and logins brought over in one step, and a browser that keeps getting updates.
Questions
Do Chrome extensions work in Rio and SigmaOS?
In Rio they run as they do in Chrome, because Rio is built on Chromium. SigmaOS runs on WebKit and wrote its own version of the Chromium extension API, and its Arc guide says you might face compatibility issues.
Do my Arc passwords come over?
In Rio, yes, in the same step as everything else: macOS asks once before Rio reads Arc's saved passwords. SigmaOS's Arc guide lists saved passwords as later and has you export a CSV file from Arc and import it.
Is Rio still being updated?
Yes. Rio updates itself and shipped 8 releases from its launch on November 10 to build 1474 on November 12, 2026. The newest release in SigmaOS's update feed is 1.19.0, from February 4, 2025.
What does Rio cost?
Nothing. Every feature is free, and the code is open source under GPL-3.0. SigmaOS lists a free plan and paid plans at $20 and $30 a month.
Sources
- SigmaOS (WebKit engine, Chromium extensions, plans)
- SigmaOS docs, Migration Guide: From Arc to SigmaOS
- SigmaOS update feed (appcast), newest release 1.19.0 (February 4, 2025)
- Rio releases on GitHub
- Rio source, the import checklist (SwitchImport.tsx)
- Rio source, the Ask row's assistants (command/ask.ts)
- Rio source code on GitHub (GPL-3.0)
