Install Cosmos on macOS

Installing Cosmos on macOS takes three steps: get your download link, drag the app into /Applications, then strip the macOS quarantine flag so it opens. Because current builds are ad-hoc signed, you run one extra command today — it goes away in the public release.

Before you start

• Apple Silicon (M-series) is the primary, fully supported target. Intel Macs and other operating systems are in development.
• You need a download link, which is delivered by email after you join the waitlist.

1. Get a download link

Sign up on the waitlist to receive your .dmg download link by email. The link points to the latest signed build.

2. Install the app

Open the downloaded .dmg and drag Cosmos.app into your /Applications folder, just like any other Mac app.

3. Strip the quarantine flag and open

macOS quarantines apps downloaded outside the App Store. Clear the flag, then launch the app:

xattr -cr /Applications/Cosmos.app
open /Applications/Cosmos.app

After the first successful open, you launch Cosmos normally from Launchpad or the Applications folder.

Why is this manual step needed?

Current builds are ad-hoc signed. A notarised release is pending an Apple Developer certificate. Once notarised, macOS will open Cosmos without the xattr step — this manual step goes away in the public release.

Which Macs are supported?

Apple Silicon (M-series) is the primary, fully supported target. Intel Macs and other operating systems are in active development.

Is the xattr command safe?

Yes. xattr -cr recursively clears extended attributes — including the quarantine flag — on the app bundle you just installed. It does not modify the app's code or your data.

macOS still says Cosmos can't be opened — what now?

That warning is expected on ad-hoc-signed builds. Re-run xattr -cr /Applications/Cosmos.app and reopen. See Troubleshooting for more.