Roar

The open-source browser your AI agent can drive.

A Chromium sidebar browser for macOS with a built-in MCP server. Claude, Cursor or any MCP client browses in the same window you do, logins and all, in spaces you allow. Open source. Yours.

Download for macOS: Apple Silicon (Roar-<version>.dmg)  ·  Intel (Roar-<version>-intel.dmg)
Website  ·  Free, MIT licensed

_{▶ Watch the one-minute demo}

Install

About five minutes. Needs macOS 13 or later; no Node.js.

1. Download (1 min). Get the latest Roar-<version>.dmg (Apple Silicon) or Roar-<version>-intel.dmg (Intel) from Releases, open it and drag Roar onto Applications. Or:

brew install --cask roarbrowser/tap/roar

2. First open. Roar is signed and notarized by Apple, so it opens like any app you download: macOS asks once whether to open it. Click Open.

3. Connect your agent (1 min). Roar's welcome page has a Connect button for Claude Code, Claude Desktop, Cursor, VS Code, Windsurf, Codex, Gemini CLI and others. Click yours and restart that app. The MCP server ships inside Roar and launches Roar if it isn't running (keep Allow agents to connect on).

The server is /Applications/Roar.app/Contents/Resources/roar-mcp, a stdio MCP server.

claude mcp add --scope user roar -- /Applications/Roar.app/Contents/Resources/roar-mcp     # Claude Code
codex mcp add roar -- /Applications/Roar.app/Contents/Resources/roar-mcp      # Codex
gemini mcp add roar /Applications/Roar.app/Contents/Resources/roar-mcp        # Gemini CLI
code --add-mcp '{"name":"roar","command":"/Applications/Roar.app/Contents/Resources/roar-mcp"}'  # VS Code

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json), Cursor (~/.cursor/mcp.json), Windsurf (~/.codeium/windsurf/mcp_config.json) and most other clients:

{ "mcpServers": { "roar": { "command": "/Applications/Roar.app/Contents/Resources/roar-mcp" } } }

On first launch Roar offers to bring over your Arc spaces and pinned tabs. Updates arrive through Roar › Check for Updates…

Coming from Dia or legacy Arc?

We don't need a browser company to build a browser.

The Browser Company put Arc in maintenance mode in May 2025 to build Dia. If you lived in
Arc, a company decided for you that your browser was done. Dia is their answer: closed
source, with the AI they built in.

Roar is the other answer. MIT licensed, so nobody can shelve it. No built-in assistant;
bring the agent you already use and plug it in over MCP. Your spaces and pinned tabs come
over on first launch.

Built for agents

Your agent, not ours. The bundled MCP server (roar-mcp, built on
chrome-devtools-mcp) lets it open
pages, read them, click, fill forms, run scripts and take screenshots, and starts Roar if
needed. Settings > "Your AI agent drives Roar" picks where it works: this window, so you
watch (the default), or a hidden headless Roar with its own profile (~/.roar-headless,
port 9444) started on demand.

• Agents can reach you. Two extra tools put cards in the sidebar: notify_user (info,
  done, or needs-you, with an optional Open link) and ask_user, which shows buttons and hands
  your click back to the agent. Needs-you cards also raise a macOS notification and a Dock
  badge while Roar is in the background. Cards last for the session.
• Your Claude Code sessions, live in the sidebar. Turn on Settings > "Show my Claude Code
  sessions in the sidebar" (it adds a hook to ~/.claude/settings.json). Every session shows its
  project, what it's doing and whether it needs you; click one running in tmux or cmux to watch
  its terminal right under the row and reply, answer a prompt with 1/2/3, or press Esc or ⌃C.
  Others jump to their window. + This tab in that panel sends the page you're on to the
  session's prompt (never ghost tabs). New starts a session in any folder. The hook reports the
  prompt, tool and state, never the conversation.
• Agent pages are real tabs. new_page opens a tab in your active space's sidebar,
  not a stray window, so you can watch, take over, or close what the agent is doing.
• Agents per profile. Right-click a space (or use Settings) to allow or block agents in
  it. Blocked spaces and ghost tabs are hidden from CDP entirely, so agents can't list or
  attach to them; with several spaces allowed, the agent asks you which to use (or calls
  use_profile), and its new pages open there.
• One click to cut it off. The dot under the settings icon shows whether agents can
  reach the current space (hover for the port, connected agents and allowed spaces); click
  it to allow or block agents in this space. Settings > "Allow agents to connect" closes
  the CDP port entirely, without restarting.
• Looks like Chrome to sites. Roar reports the Google Chrome brand and a real window
  frame, and doesn't run polling scripts in pages, so it trips fewer bot checks.
• Also scriptable: AppleScript (open url, execute javascript, get URL of every tab)
  and raw CDP on 127.0.0.1:9222 (extra instances start at 9333).

For browsing

Tabs that stay tidy

• A vertical sidebar with pinned tabs (⌘D), pinned groups and tab groups; drag to reorder.
• Each tab has a thin bar that shrinks while you ignore it; when it runs out the tab moves to
  Archived (after 6h, 12h, 1 day or 1 week, or never). ⇧⌘K archives now, ⇧⌘T brings one back.
• ⌃Tab switches tabs most recently used first; ⌘1–⌘9 jumps straight to one.
• A speaker on tabs playing audio; click it to mute.

Spaces and privacy

• Spaces keep separate tabs and a separate profile (logins, cookies, extensions): ⌃1–⌃9 or ⇧⌘[ ⇧⌘].
• Ghost tabs (⇧⌘N) use a throwaway profile per session that Roar deletes on its next launch.
• Copy Link Address unwraps Outlook Safe Links and .mcas.ms wrappers.
• uBlock Origin Lite is built in; other Chrome extensions install as usual.

Getting around

• One command bar (⌘T, ⌘L) for addresses, search, open tabs, history and the text of pages
  you've visited. Type > for commands.
• Split view (⌘\), or drag a tab onto another: left half for side by side, right half for top and bottom.
• Reader mode (⌥⌘R), find in page (⌘F), per-site zoom, swipe back and forward.
• Picture-in-picture for video (⇧⌘P), or float any tab in a mini window (⇧⌘F).
• New windows (⌘N) start with your spaces and pinned tabs.

Small things that add up

• Copy any page as Markdown (⇧⌘C) or save it to Downloads.
• Unread Gmail in the sidebar, with Read, Move and Delete per message.
• Your open GitHub pull requests as a live folder (via gh).
• Sign-in popups open as sidebar tabs, not stray windows.
• A history page (⌘Y) with search and a day-by-day view; Reopen All Tabs from Last Session.

For developers

./scripts/build.sh                       # fetches CEF into third_party/, builds, signs (Developer ID or Apple Development identity if present, else ad-hoc)
open build/src/Release/Roar.app
./scripts/update-cef.sh                  # move to the newest stable CEF/Chromium and rebuild (--check to only report)

Needs macOS, Xcode, cmake and ninja. Environment overrides:

• ROAR_CDP_PORT (default 9222): DevTools Protocol port; setting it also forces the port on.
  The port is on by default; Settings > "Allow agents to connect" opens or closes it while
  Roar runs.
• ROAR_DATA_DIR (default ~/Library/Application Support/Roar): profile and state.json.
• --load-extension=<dir>: load an unpacked Chrome extension. It loads into every Space's profile, alongside the bundled uBlock Origin Lite.

CEF binds a Chrome-style window to the first Chrome-style BrowserView it hosts, so
Roar uses a frameless Alloy shell window for the sidebar and one frameless Chrome-style
window per tab, attached as a macOS child window over the content area. The command bar
and toast are small Alloy child windows. Chrome style on tabs is what keeps extensions,
DevTools and CDP working. See src/controller.h.

The UI is HTML in resources/ui, served from roar://ui/, and talks to C++ through the
CEF message router (window.roarQuery). Web pages may only send extract.result or index.result with a
nonce Roar issued to that tab.

Known limits

• Page-text search stores page text unencrypted in the data dir (mode 0600). Turn it off in Settings, or clear it with "Forget saved text" there ("Forget saved page text" in the command bar).
• H.264 and AAC need a CEF built with proprietary codecs. The stock CEF that scripts/build.sh fetches plays WebM, VP9 and AV1 but not many .mp4 sources;
  scripts/build-cef-codecs.sh builds one that does, with Roar's Chromium patches (hours for a first build, about 30 minutes incremental; the checkout needs about 100 GB).
• The tab sound indicator follows <audio> and <video> elements on the page itself, not Web Audio or media inside cross-origin iframes.
• Markdown extraction and Reader mode cover HTML pages; PDFs and Google Docs canvases are not handled.
• The first AppleScript call triggers a macOS Automation
  prompt.

Contributing

The source is right here. Issues and pull requests welcome. Build with ./scripts/build.sh
before sending a change; UI-only edits reach the app bundle only through that script.

License

Roar is released under the MIT License. The build fetches third-party code
that keeps its own license: CEF (BSD) and
uBlock Origin Lite (GPLv3).