rac vision

rac is a private, fast, and beautiful browser for macOS. It has Arc's best ideas and Dia's calm, and an optional AI that feels right when you want it and stays out of the way when you don't.

rac is built on Helium, which is built on ungoogled-chromium. Helium provides privacy and speed. rac adds the interface, features, and polish on top.

The name is "arc" backwards. It's written in lowercase: rac.

Why rac exists

Arc changed how browsing felt, then got buggy, glitchy, and slow, and eventually stopped being developed. Dia was clean and calm, but not agentic enough. Aside could actually control the browser, but it felt slow and cluttered. Helium is private, fast, and clean enough, but plain. Most browsers that copy Arc feel unfinished and slow. The few with AI do it badly.

rac is the browser that should exist: Helium's privacy and speed, Arc's features and beauty, Dia's simplicity, and AI that is genuinely useful without being in your face. It's also open source, because a browser sees everything you do, and you should be able to read its code.

Who it's for

rac is the maintainer's daily driver first. It's kept up to date with Helium and improved continuously. Everyone else is welcome, especially:

• former Arc users looking for a replacement
• Helium users who want a nicer interface
• anyone who wants a browser that feels good to use

What rac never compromises on

1. Private. rac never sees, keeps, or sells your data. There are no rac accounts, no rac servers holding your browsing, no ads, and no sponsored content. When you use AI, your chosen provider's terms apply between you and that provider. rac itself never sees your conversations. The one thing rac may ever receive is a crash report, only if you turn crash reports on, and only when you say yes after that crash.
2. Never slower than Helium. Every feature has to earn its place without slowing startup, tab switching, scrolling, or typing. Features that are turned off cost nothing: no background work, no network calls, no processes.
3. Beautiful and calm. Arc's playful color and personality, combined with Dia's simplicity and elegance. Tasteful micro-interactions that make the browser feel alive, never animation for its own sake.
4. Opinionated. Like Arc and Dia, rac picks good defaults instead of offering a setting for everything. A setting exists only when people genuinely need different behavior.
5. AI is optional and quiet. AI is off until you turn it on. When it's on, it shows up only where it's useful. It shows what it's doing in a calm, minimal way, and it never takes an action you didn't ask for.
6. Open. rac is GPL-3.0, developed in the open, and tracks Helium closely instead of drifting into a separate codebase.

How rac works

Profiles, spaces, and tabs

• Each profile opens in its own window, the same as in Helium. Profiles keep logins, cookies, and data separate.
• Each profile has its own spaces. A space is a separate set of tabs with its own color theme and icon. You switch spaces with the dots at the bottom of the sidebar.
• Favorites sit at the top of the sidebar as icons. They are shared by every space in a profile. Helium calls these "pinned" today.
• Pinned tabs are Arc-style. They live in the sidebar of one space, stay there permanently, and are separate from that space's regular open tabs. They can sit loose or inside folders. Each pinned tab remembers the page it was pinned on, so you can browse away and then reset it back.

The sidebar

• Tabs live in a vertical sidebar, building on Helium's vertical layout.
• Cmd+S turns frameless mode on and off, which fully hides and shows the sidebar.
• While the sidebar is hidden, moving the mouse to the left edge of the screen shows the full sidebar over the page. Moving it to the top edge reveals the hidden toolbar. This builds on Helium's existing behavior and makes it feel polished.
• An appearance setting moves the address bar into the sidebar.

Everything else

• Command bar: a quick launcher for tabs, history, and actions. ⌘T and ⌘L open it; one setting gives ⌘T back to the regular new tab page.
• Boosts: restyle any website with your own CSS and JavaScript.
• Space themes: gradient color themes, one per space.
• Split view: several tabs side by side (Helium has this today).
• Picture-in-picture that pops out automatically when you leave a tab with a playing video.
• Media controls in the sidebar.

AI

AI is a core part of where rac is going. These points hold:

• AI is off by default. Onboarding asks whether you want it, and you can change your answer in settings at any time.
• When AI is off, none of its code does any work.
• rac never sees your AI conversations, and rac doesn't run its own AI servers.
• The AI never does anything risky in your browser (sending, buying, deleting, signing in) without asking you first. You choose how much it asks about everything else.

The AI comes from your own API key, a local model, or an agent you already use, such as Claude Code or Codex. How it works, including the agent and its safety checks, is in docs/internals/ai.md.

What rac will never do

• Collect, keep, sell, or look at your data
• Show ads or sponsored content
• Require an account
• Include a built-in VPN
• Include crypto features

Not planned for now

These aren't ruled out forever, just not on the roadmap:

• Auto-archiving old tabs
• Peek-style link previews in a floating window
• A settings page for everything
• A second, more Arc-like layout for spaces and profiles: one window where each space picks a profile, switchable with today's layout (maybe later; see the roadmap)
• Sync (maybe later)
• Linux and Windows (maybe someday)
• iOS (probably someday)

Relationship with Helium

rac follows Helium releases closely, and all of rac's changes sit on top of Helium as a separate layer. When Helium adds something rac also built, rac should consider adopting Helium's version. rac is an independent project. It is not affiliated with Helium, and rac issues and contributions never go to Helium's repositories.

See the roadmap for the order in which this gets built.