Error 499

499 Client Close Request

The HTTP 499 error typically occurs when a client terminates the connection before the server is able to respond.

Common use cases

Examples of 499 errors include situations where a client times out and closes the connection before the server completes processing, such as during large file uploads or long-running requests. They can also occur due to issues in the TCP three-way handshake, where the client terminates the connection prematurely because of its timeout settings.

Cloudflare-specific information

The 499 Client Closed Request status code is specific to nginx and indicates that the client closed the connection while the server was still processing the request, preventing the server from sending a status code in response. This status code appears in Cloudflare Logs and status code analytics for Enterprise customers.

Note

Since Cloudflare is built on nginx, the 499 HTTP code is also logged in Cloudflare Logs and analytics for connections terminated by clients before Cloudflare has finished processing the request. It is expected to occasionally see these entries in your logs as clients close connections.

To provide more context, a TCP connection must be established between Cloudflare and the website's origin server before any higher protocol (such as HTTP) begins communication. TCP uses a three-way handshake to establish connection:

• SYN: Cloudflare sends a SYN packet to the origin server.
• SYN+ACK: The origin server responds with a SYN+ACK packet.
• ACK: Cloudflare sends an ACK packet back to the origin server.

At this point, the connection is established, and both Cloudflare and the origin server can communicate. However, if the origin server does not send a SYN+ACK back to Cloudflare within 15 seconds, Cloudflare retries once more, with another 15-second timeout.

Depending on the client-side timeout settings, the following scenarios can occur:

• Shorter client timeout (less than 30 seconds): If the client has a shorter timeout, it will abandon the connection before Cloudflare completes processing, and a 499 error will be logged.
• Successful connection (more than 30 seconds): If the client has a longer timeout and the TCP connection is successfully established, the HTTP transaction proceeds normally, and Cloudflare returns a standard status code (HTTP 200).
• Handshake failure: If the client has a longer timeout but Cloudflare cannot establish the TCP handshake with the origin server, Cloudflare will return an HTTP 522 status code.