HTTP 303 See Other vs 499 Client Closed Request
HTTP 303 (See Other) is a 3xx Redirection response, while 499 (Client Closed Request) is a 4xx Client Error response. 303 indicates that the server is redirecting to a different resource using GET, typically after a POST operation (Post/Redirect/Get pattern). In contrast, 499 means that a non-standard status code used by Nginx when the client closes the connection before the server responds.
Description
The server is redirecting to a different resource using GET, typically after a POST operation (Post/Redirect/Get pattern).
When You See It
After form submissions to prevent resubmission on browser refresh.
How to Fix
Follow the Location header with a GET request. This is intentional — part of the PRG pattern.
Description
A non-standard status code used by Nginx when the client closes the connection before the server responds.
When You See It
In Nginx logs when clients timeout or navigate away before receiving the response.
How to Fix
Optimize server response times. Check for slow upstream services.
Key Differences
303 is a 3xx Redirection response, while 499 is a 4xx Client Error response.
HTTP 303: The server is redirecting to a different resource using GET, typically after a POST operation (Post/Redirect/Get pattern).
HTTP 499: A non-standard status code used by Nginx when the client closes the connection before the server responds.
You encounter 303 when after form submissions to prevent resubmission on browser refresh.
You encounter 499 when in Nginx logs when clients timeout or navigate away before receiving the response.
When to Use Which
For 303 (See Other): Follow the Location header with a GET request. This is intentional — part of the PRG pattern. For 499 (Client Closed Request): Optimize server response times. Check for slow upstream services.