CRL is an extension given to files used in certification mechanisms in Windows operating systems. They are used to control access to specific resources on the network. This solution is based on a public key infrastructure. The CRL file stores the list of certificates that have been revoked by the publisher. It contains their serial numbers and the reasons for revoking the certificate.

Due to the necessity of frequent updating of CRL lists, this solution was replaced with the OSCP mechanism, which allows to verify the validity of certificates on-line.