rac

A private, fast, and beautiful browser for macOS, with Arc's best ideas, Dia's calm, and optional AI that feels right.

rac is a fork of helium-macos, built on Helium. It tracks Helium's releases and adds its own changes as a separate layer of patches on top.

Status: early development. rac has its own name and its first features, such as spaces, pinned tabs, and the optional AI assistant, but there are no public builds yet. See the roadmap.

rac is an independent project. It isn't affiliated with or endorsed by Helium, imput, or The Browser Company. Please don't report rac issues to Helium.

What rac is going for

• Private: no data collection, no accounts, no ads, ever.
• Fast: never slower than Helium.
• Beautiful: Arc's personality with Dia's simplicity.
• Arc's best ideas: spaces, favorites, pinned tabs, a sidebar that gets out of the way, a command bar, and boosts.
• AI, only if you want it: off by default, quiet when on. Bring your own API key, a local model, or an agent you already use, such as Claude Code or Codex. It asks before it acts.

Read the full vision.

How it works

rac builds Chromium from source in layers:

1. Chromium
2. ungoogled-chromium patches
3. Helium core patches (the helium-chromium/ submodule)
4. Helium macOS patches
5. rac patches (patches/rac/)

Because rac keeps its changes in its own patches, picking up a new Helium release means merging helium-macos and refreshing rac's patches. Details are in the docs.

Building

Follow docs/building.md, but clone rac instead of helium-macos:

You need macOS, Xcode, and over 100 GB of free disk space. A full build takes several hours.

Contributing

Contributions are welcome, including AI-assisted ones, as long as they're run in a real build and shown with screenshots. Agents test it themselves; they don't hand first look to the maintainer. Read CONTRIBUTING.md. Bugs, ideas, and questions all go in Issues.

Credits

Helium

rac is built on Helium and helium-macos by imput. Almost everything that makes rac work is their work.

ungoogled-chromium

Helium is based on ungoogled-chromium and ungoogled-chromium-macos.

Arc and Dia

rac's design is inspired by Arc and Dia from The Browser Company.

License

rac is licensed under GPL-3.0, the same as Helium. See LICENSE.

Content imported from other projects keeps its original license. For example, unmodified code from ungoogled-chromium stays under its BSD 3-Clause license.