How to Set Up SSH Keys for GitHub, Linux, Mac, and Windows

Set up SSH keys step by step: generate a key pair, install the public key, configure ssh-agent, add keys to GitHub or GitLab, and fix common errors.

Setting up SSH requires generating a key pair, installing the public key, and testing the connection.
Do not disable password authentication until key-based login has been verified.
Use ssh-agent or the macOS Keychain to manage passphrases for personal keys.