HTTP 415 UNSUPPORTED MEDIA TYPE

The server does not accept this Content-Type or Content-Encoding. 415 belongs to the 4xx client error class and is defined in RFC 9110.

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About HTTP 415

What Does HTTP 415 Unsupported Media Type Mean?

The server does not accept this Content-Type or Content-Encoding. The code is registered with IANA and defined in RFC 9110.

Client error: the request has a problem, so it cannot be fulfilled as sent. Every code from 400 to 499 shares that general meaning, so a client that does not recognise 415 must treat it like 400.

When Do You See a 415 Response?

415 Unsupported Media Type means the server will not accept the request body in the format declared by Content-Type, or with the Content-Encoding applied. Typical cases are sending form data to a JSON-only API, forgetting the Content-Type header entirely, or posting XML to an endpoint that only parses JSON. It also appears when a body is gzip-compressed but the server does not support compressed requests.

How Do You Fix a 415?

Set the Content-Type header to match the body exactly, usually application/json for JSON APIs. A common trap is curl's -d option, which labels data as form-urlencoded unless you add the header; the 2http Request builder adds it for JSON bodies. Servers should list the accepted types in an Accept response header (or Accept-Encoding for unsupported compression).

What Does a 415 Response Look Like?

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

415 is not cacheable by default: a browser or CDN stores it only when Cache-Control or Expires explicitly allows it.

To inspect a real one without sending it anywhere:

Copy the response headers from your browser Network tab, or from curl -i.
Paste them into the Header decoder to see every header explained.
Check caching in the Cache lane.

Which Status Codes Are Related to 415?

406 Not Acceptable: No representation matches the Accept headers the client sent.
400 Bad Request: The request is malformed: bad syntax, invalid framing, or an unreadable body.
422 Unprocessable Content: The syntax is fine but the content fails validation. Common in JSON APIs.

Browse every code on the HTTP status codes page.

What Other Lanes Are in the Reference Section?

HTTP status codes: Every IANA-registered status code, with a page per code.
MIME types: File extensions to Content-Type, searchable both ways, plus a Content-Type parser.
HTTP methods: GET, POST, PUT, PATCH, DELETE and the rest: safe, idempotent, cacheable.

Elsewhere in 2http: Header decoder, Cookie decoder, Cache-Control decoder, CORS checker, User-agent parser, and all eleven lanes on the 2http home page. Part of the 2suite.io privacy-first ecosystem.

Frequently Asked Questions

Why does my curl POST get 415?

curl -d sends data as application/x-www-form-urlencoded by default. If the API expects JSON, add a Content-Type: application/json header or use curl's --json option.

What header should accompany a 415?

RFC 9110 suggests Accept or Accept-Encoding in the response, telling the client which media types or content codings the server would accept.

Is HTTP 415 an error?

Yes. 415 is a client error response: the problem is in the request, so repeating it unchanged will usually fail again.

Is a 415 response cacheable by default?

No. Caches store a 415 only when Cache-Control or Expires explicitly allows it.

How Can You Verify That Nothing Leaves This Browser?

You do not have to take our word that your headers stay here. Developer tools show every request a page makes, so you can watch this page work and confirm that nothing is sent. The check takes under a minute.

Open your browser developer tools with F12, or Cmd+Option+I on a Mac, and select the Network tab.
Reload the page and let it finish. You will see the page's own files, its web fonts, and one anonymous page-view request. Nothing has been typed yet, so none of them can contain your headers.
Click the clear icon in the Network tab so that the log is empty.
Paste real headers into any lane and read the result.
Look at the Network tab again. It is still empty. For extra proof, turn on offline mode after the page loads and every lane keeps working.

Only two things can add a line to that log, and neither carries your headers. Submitting the feedback form sends the vote and comment you typed. Typing characters in a script the page has not displayed yet, such as Cyrillic or Greek, can make the browser fetch the matching font file, and that request names only the font.

2http never sends a request on your behalf: the request builder writes code for you to run, and the meta inspector reads source you paste instead of fetching a URL. The production site also sends a Content-Security-Policy header that tells your browser to refuse connections to anywhere except this site and the anonymous analytics endpoint.

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