According to CoinMeta, Tailscale has open-sourced Tailcat. Users do not need to register an account or join the same tailnet; they only need to obtain a connection address to directly connect two machines. This tool continues to use Tailscale's WireGuard encryption, NAT penetration, and DERP relay, but it does not require Tailscale's account or control panel. The machine running Tailcat will generate a connection address, which users can use to transfer files, forward ports, or establish a SSH connection. The connection process first finds the other party through DERP, then attempts to establish a peer-to-peer UDP connection. If the tunneling fails, traffic is relayed through DERP. Tailscale's chief engineer, Brad Fitzpatrick, created a prototype of Tailcat as early as 2023. Recently, the project was restarted due to AI and the large number of connections to sandboxes, remote VM, and test machines. Tailcat is not a complete substitute for Tailscale; it lacks user identity management, permission policies, and device management. Connection addresses must be properly kept secure.