Via HTTPS For those checking out sources as read-only, HTTPS works best: git clone https://github.com/apple/swift.git ./swift/utils/update-checkout --clone Via SSH For those who plan on regularly making direct commits, cloning over SSH may provide a better experience (which requires uploading SSH keys to GitHub): git clone git@github.com:apple/swift.git ./swift/utils/update-checkout --clone-with-ssh