Content Negotiation#

Content negotiation is a mechanism defined in the HTTP specification that makes it possible to serve different versions of a document (or more generally, a resource representation) at the same URI, so that user agents can specify which version fit their capabilities the best.

The user agent (or the REST consumer) can ask for a specific representation by providing an Accept HTTP header that lists acceptable media types (e.g., JSON):

GET /
Accept: application/json

The server is then able to supply the version of the resource that best fits the user agent's needs. This is reflected in the Content-Type header:

HTTP 200 OK
Content-Type: application/json

{
  'data': ...
}