Ordnance Survey Authentication
Three interchangeable credentials across the whole Ordnance Survey estate: the Project API Key as the `key` query parameter, the same key as the `key` request header, or an OAuth 2.0 client-credentials Bearer token. Credentials belong to an OS Data Hub API Project, not to a user, and carry no scopes - entitlement comes from which APIs are attached to the project and which plan the account holds. A 401 is a credential failure; a 403 is a LICENSING failure. The OS Net API spec ships an unresolved OAUTH_TOKEN_URL placeholder as its tokenUrl; the real endpoint is https://api.os.uk/oauth2/token/v1.
Ordnance Survey secures its APIs with apiKey and oauth2 across 3 declared security schemes, as derived from its OpenAPI definitions. OAuth 2.0 is offered via the clientCredentials flow(s).