The Online Certificate Status Protocol (OCSP) allows a client to query a certificate authority's OCSP responder to check the real-time revocation status of a specific certificate, rather than downloading and parsing an entire Certificate Revocation List (CRL). OCSP responses are typically much smaller and faster to process than CRLs, especially as the number of revoked certificates grows, though OCSP does introduce a dependency on the availability of the OCSP responder at validation time, which OCSP stapling helps address.