Content-Type vs Accept HTTP Headers — Request and Response Format

Direct Answer

Content-Type describes the representation carried by the current message body. Accept lists response media types the client can accept. A request with an unsupported body Content-Type can produce 415, while an endpoint unable to produce any acceptable response type can produce 406. Not every request has a body, so Content-Type is not required on every call.

Code Example

var restTemplate = new RestTemplate();
var headers = new HttpHeaders();

// Content-Type: what format am I sending?
headers.setContentType(MediaType.APPLICATION_JSON);

// Accept: what format do I want back?
headers.setAccept(List.of(MediaType.APPLICATION_XML));

var order = new Order(null, "Laptop", 1299.99);
var request = new HttpEntity<>(order, headers);

// Sends JSON (Content-Type), expects XML back (Accept)
var response = restTemplate.postForEntity(
    "http://localhost:8080/api/orders",
    request,
    Order.class
);

// Server sees Content-Type: application/json -> deserializes request as JSON
// Server sees Accept: application/xml -> serializes response as XML

Common Mistakes & Pitfalls

• Using Content-Type to request response format: Freshers often think setting Content-Type: application/xml will make the server return XML. Content-Type only describes what you're sending, not what you want back—that's Accept's job.
• Forgetting Content-Type on POST requests: Sending JSON data without Content-Type: application/json causes 415 errors because Spring doesn't know how to parse the body. The header isn't optional when there's a body.
• Expecting Accept to affect request parsing: Setting Accept: application/xml doesn't change how Spring reads your request body—it only affects the response. If you send JSON, you still need Content-Type: application/json regardless of your Accept value.