reverse lookup API

A “reverse lookup” finds a prefix for a given namespace URI. You can perform reverse lookups by entering a namespace URI into the box on the start page, or by using the reverse lookup API.

Query URL:

GET query parameters:
uri – URLencoded namespace URI
format – any of the supported formats (optional)


“Bulk lookup” of many URIs in a single request is not supported by the URIs. Please download the entire namespace data and perform bulk operations locally.