Flashing with a wrong auth bypass can:

Legitimate access to XAT is sold via credits or daily subscriptions on websites like XiaomiAuth.com (note: URLs change frequently). Typical pricing:

You pay, receive a login to a remote server or a license key, and the tool works via their live servers.

The Xiaomi Auth Tool is a small, specialized Windows-based utility designed to bypass Xiaomi’s server-side authentication requirement. When a Xiaomi device is put into EDL Mode (Emergency Download Mode), tools like Mi Flash or SP Flash Tool usually require a user to log in with an authorized Mi Account.

XAT acts as a middleware or "bypass" agent. It tricks the flashing tool and the device into believing the authentication handshake has been successfully completed with Xiaomi’s servers, allowing the technician to flash Stock ROMs (Fastboot firmware) without needing an authorized login.

Searching “XAT free download” is dangerous. Most free versions are either:

Warning: Never run an unidentified .exe file from a YouTube video description on your main computer.