HTTP API

sparqld exposes one read-only SPARQL query endpoint at /.

Query requests

The endpoint accepts the SPARQL Protocol GET form and both standard POST forms.

Method	Query encoding	Content type
GET	URL-encoded query parameter
POST	SPARQL query in the request body	application/sparql-query
POST	URL-encoded query parameter in the request body	application/x-www-form-urlencoded

A plain GET / returns a text landing response.

Startup

sparqld binds its HTTP listener before it finishes the initial directory load. Requests at / wait until that load has published its first dataset, so the first ordinary query can be the readiness wait. Set the HTTP timeout in the client; sparqld does not impose a startup wait deadline.

File-level load errors remain visible in the file catalog and do not prevent the first dataset from becoming ready. A fatal initialization error marks root requests unavailable with 503 Service Unavailable before sparqld exits nonzero; because the process exits immediately, a caller can instead observe a dropped connection.

Responses

Query form	Content type	Body
SELECT	application/sparql-results+json	SPARQL Query Results JSON
ASK	application/sparql-results+json	SPARQL Query Results JSON
CONSTRUCT	text/turtle	Turtle graph
DESCRIBE	text/turtle	Turtle graph

The response serialization is selected by the query form. Accept headers do not currently negotiate another representation.

Errors and limits

Status	Condition
400 Bad Request	Missing, repeated, malformed, or invalid query
404 Not Found	Request path other than /
405 Method Not Allowed	SPARQL Update or another unsupported HTTP method
413 Payload Too Large	Query body exceeds 1 MiB
415 Unsupported Media Type	Unsupported POST Content-Type
503 Service Unavailable	Fatal initial dataset failure before process exit
500 Internal Server Error	Query evaluation or serialization failure

Error bodies are text/plain. A 405 response includes Allow: GET, POST. Change RDF by editing the served files; SPARQL Update is rejected permanently.