Where is the unique fingerprint identifier of the key stored when establishing an SSH connection?

The unique fingerprint of an SSH connection key is stored in the known_hosts file on the client machine. This file is usually located in the user's directory at ~/.ssh/known_hosts. When connecting to a server for the first time, SSH saves the server's public key fingerprint in this file to verify the server's authenticity in subsequent connections and prevent man-in-the-middle attacks.