415 Unsupported Media Type: causes and the fix

A 415 Unsupported Media Type error means the server refused your request because it doesn't accept the format of the body you sent. The fix is to send the body in a format the endpoint accepts and label it with a matching Content-Type header; for a JSON API, that means a JSON body with Content-Type: application/json.

The HTTP definition is quoted from MDN's 415 Unsupported Media Type page and each client's defaults from its own docs; the Sume behavior comes from its Errors and spend and Create a run docs. All were read on 2026-09-27.

Why am I getting 415 Unsupported Media Type?

Because of how the body is labeled or encoded. MDN says the problem may come from the request's Content-Type or Content-Encoding, or from the server processing the content itself. Its two examples are the everyday ones: a JSON body sent with no Content-Type header at all, and a JSON body labeled application/x-www-form-urlencoded.

Some servers are strict about the exact value, too. MDN's example: writing UTF8 instead of UTF-8 for the charset can make a server consider the media type invalid.

Switching to multipart/form-data to attach a file is the same mistake on a JSON API. On Sume, generation requests take media as public HTTPS URLs inside the JSON body instead.

How do I fix 415 in curl, fetch, axios, and Python Requests?

Each client picks a Content-Type when you don't set one, and that default is what the server sees:

What does Sume's 415 response tell me?

Sume's API takes JSON request bodies: every create needs Content-Type: application/json, and its docs list 415 unsupported_media_type for a body that was not sent as application/json. The error echoes the type the server received in details.received_content_type, and today it also lists what the API accepts in details.supported. In current code, a curl -d call without the header gets a response like this (abridged):

{
  "error": {
    "code": "unsupported_media_type",
    "message": "Send the request body as application/json.",
    "retryable": false,
    "next_action": "fix_input",
    "details": {
      "received_content_type": "application/x-www-form-urlencoded",
      "supported": ["application/json"]
    }
  }
}

Should I retry a 415?

Not as is. The same body with the same header gets the same answer, and today the error is marked not retryable, with next_action set to fix_input. On a Format run create, a 4xx means nothing ran and nothing was charged, so fix the header and send again.

Is unsupported_media_type from a media tool the same error?

No. On Sume's trim, filter and audio-detach tools, the same error.code means the video_url you passed does not serve a video: the tool's HEAD check of the file found another type. In current code that refusal comes back as HTTP 400, not 415, and it is about the file, not your request's header. Those tools take a video on Sume's media host, such as an earlier Sume job's output. The error index by surface lists the other codes, and the headers reference covers every header the API reads.