4×× CLIENT ERROR

444 CONNECTION CLOSED WITHOUT RESPONSE

A non-standard status code used to instruct nginx to close the connection without sending a response to the client, most commonly used to deny malicious or malformed requests.

This status code is not seen by the client, it only appears in nginx log files.

Source: nginx documentation

Recommended:

• 431 REQUEST HEADER FIELDS TOO LARGE
• 429 TOO MANY REQUESTS