I use Homebrew on my mac to manage packages. Homebrew Cask is a way to extend homebrew to manage packaged binaries. There’s an annoying (and correct) problem that when you install something like iterm2-nightly, or chromium, or mpv with homebrew cask, the first time you try to run it, you’ll get a warning that the developer cannot be verified, and then you’re given the option to delete the app, or close the warning. But the app doesn’t start.

There are a few ways to deal with this:

  1. Install it without homebrew in the first place! 
     brew install --no-quarantine chromium

    or

     brew cask install --no-quarantine chromium

    https://github.com/Homebrew/homebrew-cask/blob/HEAD/USAGE.md#options

    and

    https://docs.brew.sh/FAQ#why-cant-i-open-a-mac-app-from-an-unidentified-developer

  2. Find the app’s install dir, right click on the .app file, and hit “Open”

  3. From the terminal, take it out of jail: 
     xattr -d com.apple.quarantine /Applications/Chromium.app
  4. Remove the Quarantine Flag set by homebrew: 
     xattr -cr /Applications/Chromium.app