415 Unsupported Media Type means the origin server refuses the request because the content is in a format that this method and resource do not support. The problem can be the Content-Type (for example XML sent to a JSON-only endpoint), the Content-Encoding (for example a gzip-compressed request body) or the data itself.
The server can help the client by sending an Accept header in the response to list the media types it accepts, or Accept-Encoding when the problem is an unsupported content coding.
Do not confuse it with 406, which is about the response format the client asked for.
Example response
HTTP/1.1 415 Unsupported Media Type
Date: Fri, 06 Nov 2026 10:15:32 GMT
Accept: application/json
Content-Type: application/json
Content-Length: 49
{"error":"Content-Type must be application/json"}SEO and redirect checking
Crawlers send no request bodies, so 415 has no SEO impact. In a redirect check with the method set to POST, a 415 means the target expects a different Content-Type. Add it under Custom Request Headers, for example Content-Type: application/json.
Common causes and use cases
- A JSON API received a body without
Content-Type: application/json. - A form posts
multipart/form-datato an endpoint that only accepts JSON, or the other way round. - The request body is compressed with an encoding the server does not support.