HTTP 303 See Other vs 415 Unsupported Media Type
HTTP 303 (See Other) is a 3xx Redirection response, while 415 (Unsupported Media Type) 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, 415 means that the server refuses to accept the request because the Content-Type is not supported.
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
The server refuses to accept the request because the Content-Type is not supported.
When You See It
When sending JSON to an endpoint that only accepts XML, or missing the Content-Type header.
How to Fix
Set the correct Content-Type header matching the data format you're sending.
Key Differences
303 is a 3xx Redirection response, while 415 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 415: The server refuses to accept the request because the Content-Type is not supported.
You encounter 303 when after form submissions to prevent resubmission on browser refresh.
You encounter 415 when when sending JSON to an endpoint that only accepts XML, or missing the Content-Type header.
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 415 (Unsupported Media Type): Set the correct Content-Type header matching the data format you're sending.