EasyExperience level: 0-2 years · 3-5 years1 min read

How does HTTP content negotiation work (Accept vs Content-Type)?

Reviewed by Gurusankar M.

Asked inInfosysAccentureDeloitte
#content negotiation#accept#content-type#media type
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Short Answer

Content-Type describes the body the sender is providing; Accept tells the server what the client wants back. The server picks a representation matching Accept (or returns 406 Not Acceptable). This also powers media-type API versioning.

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“How does HTTP content negotiation work (Accept vs Content-Type)?”

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Mind Map Answer

Content-Type
format of THIS request/response body
Accept
formats the client will accept back
406
server can't meet the Accept
415
server can't read the Content-Type

Think Beyond the Expected

What If?

A client gets 415 Unsupported Media Type on a POST — what's wrong?

The client sent a body in a format the endpoint doesn't accept (or omitted/typo'd Content-Type, e.g. sending JSON without Content-Type: application/json). Set the correct Content-Type so the server picks the right parser.

Real World

Content negotiation underlies returning JSON vs CSV from the same endpoint and media-type versioning (application/vnd.myapi.v2+json); 415/406 errors are everyday API debugging.

Interviewer's Expectation

Keywords they're listening for:

  • Content-Type = body format
  • Accept = desired response
  • 406 vs 415
  • media-type versioning

Common Mistakes

  • Omitting Content-Type on JSON POSTs
  • Confusing Accept with Content-Type
  • Returning 400 where 415/406 fits

Best Practices

  • Always set Content-Type on requests with a body
  • Use Accept for negotiation
  • Return precise 406/415 codes

Follow-up Questions

  1. 406 vs 415 — which is which?
  2. How does media-type versioning use Accept?
  3. How would you serve both JSON and CSV from one endpoint?

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Plain-language foundations

I'm preparing for a software engineering interview and want to understand this from scratch, as a beginner.

Topic: HTTP Methods (REST APIs)
Interview question: "How does HTTP content negotiation work (Accept vs Content-Type)?"

Please:
1. Explain the core idea in simple, plain language, using an everyday analogy.
2. Define any technical terms you use.
3. Walk through one small, concrete example.
4. Finish with a single sentence I can easily remember.

Keep the tone friendly and assume I'm new to this topic.
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