Content negotiation

Content negotiation is the mechanism defined in the HTTP specification that allows for the delivery of different versions of a resource at the same URI. This enables the same endpoint to deliver data as HTML to a browser, but as RDF or json to an API client.

Request headers

Clients supply preferences via explicit HTTP headers, which the server audits to decide the best response format:

Accept

Defines the media types that the client is willing to receive.

• Accept: text/html (Requesting visual website)
• Accept: application/ld+json (Requesting machine-readable json-ld)
• Accept: text/turtle (Requesting standard triples via turtle)
• Accept: text/n3 (Requesting verbose RDF via notation3)
• Accept: text/csv (Requesting tabular data via csv)

Accept-Language

Informs the server about the client's language preferences (e.g., en-US, fr).

Accept-Encoding

Identifies what compression algorithms (gzip, deflate, br) the client understands.

Importance in the semantic web

In a semantic-web compliant system, URIs identifying real-world resources should behave intelligently. When a human navigates to the URI, the server employs content negotiation to render the html page. When a crawler or reasoning agent requests the exact same URI, the server can provide the structured machine graph.