HTTP 415 Unsupported Media Type

HTTP 415 Unsupported Media Type — The server refuses the request because the body's format (Content-Type) isn't supported.

Class

4xx Client Error

Defined in

RFC 9110 §15.5.16

Official

Yes (IANA registry)

Cacheable by default

No (unless Cache-Control/Expires say so)

Safe to retry

Not without changing the request

What does HTTP 415 mean?

415 Unsupported Media Type means the server refuses the request because the body is in a format the endpoint doesn't support. The server looks at the Content-Type (and sometimes Content-Encoding) header — or the data itself — and doesn't accept it.

The server may include an Accept header (for POST) or Accept-Patch header (for PATCH) listing the formats it does accept.

When is 415 used?

• Sending JSON without Content-Type: application/json (e.g. as text/plain or form data).
• Uploading a file type the endpoint doesn't accept (an image API receiving a PDF).
• Using application/merge-patch+json where only application/json-patch+json is supported, or vice versa.
• Sending a gzip-encoded body to a server that doesn't decode Content-Encoding: gzip.

Common causes of a 415

• A missing or wrong Content-Type header — by far the most common cause.
• fetch() sends a string body as text/plain;charset=UTF-8 unless you set the header.
• ASP.NET Core and Spring return 415 when a [FromBody] / @RequestBody endpoint gets a content type it has no formatter for.

How to fix 415 Unsupported Media Type

If you're visiting the site

1. Check that the file you're uploading is in a supported format (e.g. JPG/PNG instead of HEIC or WebP).
2. Convert the file and try again.

If you run the site or API (developers)

1. Set the right header: Content-Type: application/json for JSON, multipart/form-data for file uploads (let the browser set the boundary — don't set it manually with FormData).
2. On the server, return 415 with an Accept header listing supported types.
3. Use 400 for a body that claims to be JSON but isn't parseable; use 415 when the type itself is unsupported.

Returning or handling 415: server examples

await fetch("/api/items", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ name: "Widget" }),
});

// File uploads: don't set Content-Type yourself
const form = new FormData();
form.append("file", file);
await fetch("/api/upload", { method: "POST", body: form });

app.post("/api/items", (req, res, next) => {
  if (!req.is("application/json"))
    return res.status(415).set("Accept", "application/json").json({ error: "unsupported_media_type" });
  next();
}, createItem);

// app/api/example/route.ts (Next.js App Router)
export async function POST(req: Request) {
  if (!req.headers.get("content-type")?.includes("application/json"))
    return Response.json({ error: "Send application/json" }, { status: 415, headers: { Accept: "application/json" } });
  const body = await req.json();
  // ...
}

Example 415 response

HTTP/1.1 415 Unsupported Media Type
Accept: application/json
Content-Type: application/json

{"error":"unsupported_media_type","message":"Send the body as application/json"}

Related status codes

• 400 Bad RequestThe server can't process the request because it's malformed or invalid.
• 406 Not AcceptableThe server can't produce a response matching the client's Accept headers.
• 422 Unprocessable ContentThe request is well-formed, but its contents fail validation.

Related tools

• HTTP status codes — full list
• HTTP headers reference
• cURL converter
• Mock API — fake REST endpoints with custom status codes
• Webhook tester — inspect incoming requests