myArc pre-alpha nightly

System requirements

• An Apple silicon Mac. Intel Macs are not supported.
• macOS 26 or later. The glass frame requires macOS 26. It has been tested only on macOS 26.7.

First launch

1. Check the download against the SHA-256 listed with it. The two values must match.

   shasum -a 256 ~/Downloads/myArc-Nightly-2026.11.10-arm64.dmg

2. Open the DMG and drag myArc Nightly to Applications.
3. macOS blocks the first launch because the app is not notarized. Right-click myArc Nightly, choose Open, then Open again. If macOS only offers Done or Move to Trash, which macOS 15 and later usually does, open System Settings > Privacy & Security, scroll to the myArc Nightly message and choose Open Anyway.
4. Or remove the quarantine flag in Terminal and open the app normally.

   xattr -dr com.apple.quarantine "/Applications/myArc Nightly.app"

What works today

Each item was seen working in a native run or experiment note. None of it has had release testing.

• Chromium browsing, with Chromium extensions. A Manifest V3 smoke test passed; wider extension coverage is untested.
• A glass sidebar with Favorite tiles, a Space heading, pinned tabs, a New Tab row and temporary tabs below the divider, next to a rounded page card. Only the dark appearance has been compared with Arc.
• Creating, switching and renaming Spaces from the sidebar footer. Favorites are shared across the Spaces of one Profile.
• Closing a pinned tab keeps the pin.
• A command bar: Cmd+L opens it on the current address, arrows, Enter and Escape work, and new windows open it centered.
• Shortcuts: Cmd+S hides the sidebar, Cmd+Shift+T reopens a closed tab, Cmd+Shift+C copies the address and shows a Copied Current URL toast, Cmd+Shift+N opens a private window and Ctrl+Cmd+N a blank one.
• Cmd+, opens a native Settings window. General shows the default-browser banner and Advanced links to the full Chromium settings. Profiles, Links and Shortcuts are not available yet.
• Quitting with Cmd+Q needs no confirmation by default, with a setting to turn the warning on.
• Agents can drive tabs in the Agent Space through the bundled myarcctl CLI and MCP server. It is off by default. Turn it on in Settings > Advanced, and myArc asks before each new agent connects.

What does not work yet

• Importing from Arc. The importer is not implemented.
• Cmd+D to pin a tab (Cmd+D still bookmarks), folders, Auto Archive, the Archive and drag-to-pin.
• Peek, Split View and Little Arc. The Peek routing rule exists, but there is no overlay.
• Boosts, the Library, download progress in the sidebar and the Mini Player.
• The animated onboarding.
• Light mode, Reduce Transparency and fullscreen layouts are not verified.

Known limitations and safety

• Built from a Chromium 158 development revision, not a stable release.
• No automatic updates and no security updates. Install each new nightly by hand.
• From 2026.11.03 on, nightlies are signed with an Apple Developer ID that later nightlies keep. macOS asks once more for your login password so it can read the saved-data key; choose Always Allow, and newer nightlies stop asking.
• The app is signed with a Developer ID but not yet notarized by Apple.
• Recent tabs and navigation can be lost after a crash or force quit.
• Private window, Profile, cookie and credential guarantees are not verified.
• RAR downloads are not scanned by Safe Browsing, because the UnRAR license conflicts with GPL-3.0.
• No Widevine, so Netflix, Spotify and Disney+ will not play.
• H.264 and AAC are included, so most other web video plays.
• myArc is an independent project, not affiliated with Arc or The Browser Company.

Other ways to get it

• GitHub releases lists every nightly.
• Source on GitHub, with instructions to build it from source.
• GitHub issues take bug reports. Include the version, your macOS version and the steps that trigger the problem, and leave out private pages.

License and notices

myArc is licensed under GPL-3.0, see LICENSE. Chromium and other bundled components keep their own licenses. ATTRIBUTION.md records what is known, and the dependency license inventory is not yet complete.