Exchange OAuth grants for opaque access tokens
Use HTTP Basic client authentication. Supports client_credentials, authorization_code with S256 PKCE, and refresh_token. Password and implicit grants are intentionally unsupported.
POST
Exchange OAuth grants for opaque access tokens
Authorizations
Use client_id as username and client_secret as password for confidential server-side calls. The application allowed_scopes still gate each /v2 endpoint; never use this secret in browsers, mobile apps, logs, or query strings. Server integrations may alternatively send x-client-id and x-client-secret headers (the legacy x-invoiceedge-* names remain accepted).
Body
application/x-www-form-urlencoded