PostgreSQL provides infrastructure for creating custom modules to perform server-side validation of OAuth bearer tokens. Because OAuth implementations vary so wildly, and bearer token validation is heavily dependent on the issuing party, the server cannot check the token itself; validator modules provide the integration layer between the server and the OAuth provider in use.

OAuth validator modules must at least consist of an initialization function (see Seção 50.2) and the required callback for performing validation (see Seção 50.3.2).