Install

Open Porpoise the first time.

Porpoise is free, so it isn't signed through Apple's paid developer program. The first time you open it, macOS stops it and asks you to allow it in System Settings. You only do this once, and it takes about a minute. The steps are the same on macOS 15 Sequoia and macOS 26 Tahoe.

  1. Drag Porpoise to Applications

    Download Porpoise.dmg and open it. In the window that appears, drag Porpoise onto the Applications folder, then eject the disk image.

  2. Open it once, then click Done

    Open Porpoise from your Applications folder. macOS says it can't verify the app. Click Done, not Move to Trash. This step makes the Open Anyway button appear in System Settings.

  3. Click Open Anyway in Privacy & Security

    Choose Apple menu › System Settings, then Privacy & Security in the sidebar. Scroll down to Security. Next to “Porpoise” was blocked to protect your Mac, click Open Anyway.

    The button appears for about an hour after step 2. If it isn't there, open Porpoise again and come back.

  4. Confirm with your password

    macOS asks once more. Click Open Anyway, then enter your Mac login password or use Touch ID. Porpoise opens.

  5. That's it

    macOS remembers your choice. Porpoise opens normally from now on, and updates installed from inside Porpoise keep working without asking again.

Prefer Terminal?

Instead of steps 2 to 4, you can remove the download quarantine yourself:

xattr -dr com.apple.quarantine /Applications/Porpoise.app

Why does macOS ask?

macOS opens downloaded apps without asking only if they are signed with a paid Apple Developer ID and checked by Apple. Porpoise is free and has no income, so it isn't. Porpoise is open source: you can read the code and build it yourself, and every release is built by GitHub Actions from the public repository.

Requires macOS 15 Sequoia or later on a Mac with Apple silicon. Questions? Open an issue.