Yes. 4xx codes are client errors: The request contains a mistake or can't be fulfilled as sent.

4xx · Client errorNot part of the HTTP standard

HTTP 499 Client Closed Request

nginx: the client closed the connection before the server answered. Often a timeout on the client side.

Example response

HTTP

HTTP/1.1 499 Client Closed Request
Content-Type: application/json; charset=utf-8

{ "error": "Client Closed Request" }

Look up the headers shown here in the HTTP headers reference.

What does HTTP 499 mean?: Client Closed Request. nginx: the client closed the connection before the server answered. Often a timeout on the client side.
Is 499 an error?: Yes. 4xx codes are client errors: The request contains a mistake or can't be fulfilled as sent.