{
  "openapi": "3.0.0",
  "info": {
    "title": "OS Linked Identifiers API",
    "version": "1.0.0",
    "x-apievangelist-provenance": {
      "method": "searched",
      "generated": "2026-07-26",
      "assembly": "Assembled by the API Evangelist enrichment pipeline from the per-operation OpenAPI 3.0.1 documents Ordnance Survey publishes inline on each docs.os.uk technical-specification page. Paths, parameters, schemas, security schemes and responses are verbatim from those published documents; only the per-page fragments were merged into one document per API.",
      "sources": [
        "https://docs.os.uk/os-apis/accessing-os-apis/os-linked-identifiers-api/technical-specification/feature-types.md",
        "https://docs.os.uk/os-apis/accessing-os-apis/os-linked-identifiers-api/technical-specification/identifier-types.md",
        "https://docs.os.uk/os-apis/accessing-os-apis/os-linked-identifiers-api/technical-specification/identifier.md",
        "https://docs.os.uk/os-apis/accessing-os-apis/os-linked-identifiers-api/technical-specification/product-version-information.md"
      ],
      "server_url_published": [
        "${lids.api.server}/search/links/v1"
      ],
      "server_url_note": "The published fragments carry an unresolved deployment template variable; substituted with the production host documented at https://api.os.uk/search/links/v1 and in the api.os.uk link index."
    }
  },
  "servers": [
    {
      "url": "https://api.os.uk/search/links/v1"
    }
  ],
  "security": [
    {
      "ApiKeyAuth": []
    },
    {
      "OAuth2": [
        "read"
      ]
    }
  ],
  "tags": [
    {
      "name": "OS OpenData Users",
      "description": "Operations available to customers using the OpenData plan"
    }
  ],
  "paths": {
    "/featureTypes/{featureType}/{id}": {
      "get": {
        "tags": [
          "OS OpenData Users"
        ],
        "summary": "Query ID when input featureType is known",
        "description": "Returns associated Linked Identifiers, when feature type is known. Returns an object.",
        "parameters": [
          {
            "$ref": "#/components/parameters/featureIdentifier"
          },
          {
            "name": "featureType",
            "in": "path",
            "description": "Feature type of ID being queried",
            "explode": true,
            "required": true,
            "schema": {
              "type": "string",
              "enum": [
                "BLPU",
                "ORRoadNode",
                "ORRoadLink",
                "Road",
                "RoadLink",
                "Street",
                "TopographicArea"
              ]
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Search results matching criteria",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/linkedIdentifier"
                }
              }
            }
          },
          "400": {
            "$ref": "#/components/responses/BadRequest"
          },
          "401": {
            "$ref": "#/components/responses/Unauthorized"
          },
          "403": {
            "$ref": "#/components/responses/Forbidden"
          },
          "404": {
            "$ref": "#/components/responses/NotFound"
          },
          "405": {
            "$ref": "#/components/responses/MethodNotAllowed"
          },
          "429": {
            "$ref": "#/components/responses/TooManyRequests"
          },
          "500": {
            "$ref": "#/components/responses/InternalServerError"
          },
          "503": {
            "$ref": "#/components/responses/ServiceUnavailable"
          }
        }
      }
    },
    "/identifierTypes/{identifierType}/{id}": {
      "get": {
        "tags": [
          "OS OpenData Users"
        ],
        "summary": "Queries ID when input identifierType is known",
        "description": "Returns associated Linked Identifiers, when the input identifier type is known. Returns an object.\n",
        "parameters": [
          {
            "$ref": "#/components/parameters/featureIdentifier"
          },
          {
            "name": "identifierType",
            "in": "path",
            "description": "Identifier type of ID being queried",
            "explode": true,
            "required": true,
            "schema": {
              "type": "string",
              "enum": [
                "GUID",
                "TOID",
                "UPRN",
                "USRN"
              ]
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Search results matching criteria",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/linkedIdentifier"
                }
              }
            }
          },
          "400": {
            "$ref": "#/components/responses/BadRequest"
          },
          "401": {
            "$ref": "#/components/responses/Unauthorized"
          },
          "403": {
            "$ref": "#/components/responses/Forbidden"
          },
          "404": {
            "$ref": "#/components/responses/NotFound"
          },
          "405": {
            "$ref": "#/components/responses/MethodNotAllowed"
          },
          "429": {
            "$ref": "#/components/responses/TooManyRequests"
          },
          "500": {
            "$ref": "#/components/responses/InternalServerError"
          },
          "503": {
            "$ref": "#/components/responses/ServiceUnavailable"
          }
        }
      }
    },
    "/identifiers/{id}": {
      "get": {
        "tags": [
          "OS OpenData Users"
        ],
        "summary": "Query identifer",
        "description": "Query by identifier and find its associated IDs. May return more than one set of links due to the namespace overlap between UPRNs and USRNs.",
        "parameters": [
          {
            "$ref": "#/components/parameters/featureIdentifier"
          }
        ],
        "responses": {
          "200": {
            "description": "Search results matching criteria",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/linkedIdentifierSet"
                }
              }
            }
          },
          "400": {
            "$ref": "#/components/responses/BadRequest"
          },
          "401": {
            "$ref": "#/components/responses/Unauthorized"
          },
          "403": {
            "$ref": "#/components/responses/Forbidden"
          },
          "404": {
            "$ref": "#/components/responses/NotFound"
          },
          "405": {
            "$ref": "#/components/responses/MethodNotAllowed"
          },
          "429": {
            "$ref": "#/components/responses/TooManyRequests"
          },
          "500": {
            "$ref": "#/components/responses/InternalServerError"
          },
          "503": {
            "$ref": "#/components/responses/ServiceUnavailable"
          }
        }
      }
    },
    "/productVersionInfo/{correlationMethod}": {
      "get": {
        "tags": [
          "OS OpenData Users"
        ],
        "summary": "Returns product version details of the source data products",
        "description": "Returns current valid version information for identifier relationships",
        "parameters": [
          {
            "name": "correlationMethod",
            "in": "path",
            "description": "Correlation method being queried",
            "explode": true,
            "required": true,
            "schema": {
              "type": "string",
              "enum": [
                "RoadLink_TOID_TopographicArea_TOID_2",
                "Road_TOID_TopographicArea_TOID_3",
                "Street_USRN_TopographicArea_TOID_4",
                "BLPU_UPRN_TopographicArea_TOID_5",
                "RoadLink_TOID_Road_TOID_7",
                "RoadLink_TOID_Street_USRN_8",
                "BLPU_UPRN_RoadLink_TOID_9",
                "Road_TOID_Street_USRN_10",
                "BLPU_UPRN_Street_USRN_11",
                "ORRoadLink_GUID_RoadLink_TOID_12",
                "ORRoadNode_GUID_RoadLink_TOID_13"
              ]
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Returns product version information about the requested correlation",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/correlationMethodInformation"
                }
              }
            }
          },
          "400": {
            "$ref": "#/components/responses/BadRequest"
          },
          "401": {
            "$ref": "#/components/responses/Unauthorized"
          },
          "403": {
            "$ref": "#/components/responses/Forbidden"
          },
          "404": {
            "$ref": "#/components/responses/NotFound"
          },
          "405": {
            "$ref": "#/components/responses/MethodNotAllowed"
          },
          "429": {
            "$ref": "#/components/responses/TooManyRequests"
          },
          "500": {
            "$ref": "#/components/responses/InternalServerError"
          },
          "503": {
            "$ref": "#/components/responses/ServiceUnavailable"
          }
        }
      }
    }
  },
  "components": {
    "securitySchemes": {
      "ApiKeyAuth": {
        "type": "apiKey",
        "in": "query",
        "name": "key"
      },
      "OAuth2": {
        "type": "oauth2",
        "flows": {
          "clientCredentials": {
            "tokenUrl": "https://api.os.uk/oauth2/token/v1",
            "scopes": {
              "read": "Grants read access"
            }
          }
        }
      }
    },
    "parameters": {
      "featureIdentifier": {
        "name": "id",
        "in": "path",
        "description": "ID of the feature that is being matched",
        "required": true,
        "schema": {
          "type": "string",
          "minLength": 1,
          "maxLength": 36
        }
      }
    },
    "schemas": {
      "linkedIdentifier": {
        "type": "object",
        "required": [
          "linkedIdentifier",
          "correlations"
        ],
        "additionalProperties": false,
        "properties": {
          "linkedIdentifier": {
            "title": "linkedIdentifier",
            "type": "object",
            "required": [
              "identifier",
              "featureType",
              "identifierType"
            ],
            "additionalProperties": false,
            "properties": {
              "identifier": {
                "type": "string"
              },
              "featureType": {
                "$ref": "#/components/schemas/featureType"
              },
              "identifierType": {
                "$ref": "#/components/schemas/identifierType"
              }
            }
          },
          "correlations": {
            "type": "array",
            "title": "correlations",
            "items": {
              "type": "object",
              "required": [
                "correlationMethodIdentifier",
                "correlatedFeatureType",
                "correlatedIdentifierType",
                "correlatedIdentifiers"
              ],
              "additionalProperties": false,
              "properties": {
                "searchedIdentifierVersionDate": {
                  "type": "string"
                },
                "searchedIdentifierVersionNumber": {
                  "type": "number"
                },
                "correlationMethodIdentifier": {
                  "$ref": "#/components/schemas/correlationMethodIdentifier"
                },
                "correlatedFeatureType": {
                  "$ref": "#/components/schemas/featureType"
                },
                "correlatedIdentifierType": {
                  "$ref": "#/components/schemas/identifierType"
                },
                "correlatedIdentifiers": {
                  "type": "array",
                  "required": [
                    "identifier",
                    "confidence",
                    "correlationIdentifier"
                  ],
                  "additionalProperties": false,
                  "items": {
                    "type": "object",
                    "properties": {
                      "identifier": {
                        "type": "string"
                      },
                      "versionNumber": {
                        "type": "number"
                      },
                      "versionDate": {
                        "type": "string"
                      },
                      "confidence": {
                        "type": "string"
                      },
                      "correlationIdentifier": {
                        "type": "string"
                      }
                    }
                  }
                }
              }
            }
          }
        }
      },
      "featureType": {
        "type": "string",
        "enum": [
          "BLPU",
          "ORRoadNode",
          "ORRoadLink",
          "Road",
          "RoadLink",
          "Street",
          "TopographicArea"
        ]
      },
      "identifierType": {
        "type": "string",
        "enum": [
          "GUID",
          "TOID",
          "UPRN",
          "USRN"
        ]
      },
      "correlationMethodIdentifier": {
        "type": "string",
        "enum": [
          "RoadLink_TOID_TopographicArea_TOID_2",
          "Road_TOID_TopographicArea_TOID_3",
          "Street_USRN_TopographicArea_TOID_4",
          "BLPU_UPRN_TopographicArea_TOID_5",
          "RoadLink_TOID_Road_TOID_7",
          "RoadLink_TOID_Street_USRN_8",
          "BLPU_UPRN_RoadLink_TOID_9",
          "Road_TOID_Street_USRN_10",
          "BLPU_UPRN_Street_USRN_11",
          "ORRoadLink_GUID_RoadLink_TOID_12",
          "ORRoadNode_GUID_RoadLink_TOID_13"
        ]
      },
      "linkedIdentifierSet": {
        "type": "object",
        "required": [
          "linkedIdentifiers"
        ],
        "additionalProperties": false,
        "properties": {
          "linkedIdentifiers": {
            "type": "array",
            "title": "linkedIdentifiers",
            "items": {
              "$ref": "#/components/schemas/linkedIdentifier"
            }
          }
        }
      },
      "correlationMethodInformation": {
        "type": "object",
        "required": [
          "methodIdentfier",
          "productCreationDate",
          "identifier1Source",
          "identifier2Source"
        ],
        "additionalProperties": false,
        "properties": {
          "methodIdentifier": {
            "$ref": "#/components/schemas/correlationMethodIdentifier"
          },
          "productCreationDate": {
            "type": "string"
          },
          "productPublicationName": {
            "type": "string"
          },
          "identifier1Source": {
            "$ref": "#/components/schemas/identifierSource"
          },
          "identifier2Source": {
            "$ref": "#/components/schemas/identifierSource"
          }
        }
      },
      "identifierSource": {
        "type": "object",
        "required": [
          "productName",
          "productPublicationDate",
          "featureType",
          "identifierType"
        ],
        "additionalProperties": false,
        "properties": {
          "productName": {
            "type": "string",
            "enum": [
              "AddressBase Premium",
              "OS MasterMap Highways Network - Roads",
              "OS MasterMap Topography Layer",
              "OS Open Roads"
            ]
          },
          "productPublicationDate": {
            "type": "string"
          },
          "productPublicationName": {
            "type": "string"
          },
          "featureType": {
            "$ref": "#/components/schemas/featureType"
          },
          "identifierType": {
            "$ref": "#/components/schemas/identifierType"
          }
        }
      }
    },
    "responses": {
      "BadRequest": {
        "description": "E.g. missing query parameter, malformed syntax."
      },
      "Unauthorized": {
        "description": "The client has not provided authentication or incorrect authentication."
      },
      "Forbidden": {
        "description": "The client has authenticated its access but does not have sufficient rights to complete the request."
      },
      "NotFound": {
        "description": "The server has not found anything matching the Request-URI."
      },
      "MethodNotAllowed": {
        "description": "Request used an unsupported HTTP method, e.g. DELETE or PUT."
      },
      "TooManyRequests": {
        "description": "Exceeded the number of requests per minute (rate-limit)."
      },
      "InternalServerError": {
        "description": "Generic internal server error."
      },
      "ServiceUnavailable": {
        "description": "Temporary outage due to overloading or maintenance."
      }
    }
  }
}