Let’s Encrypt is turning on new infrastructure to support revoking certificates via Certificate Revocation Lists. Despite having been largely supplanted by the Online Certificate Status Protocol for over a decade now, CRLs are gaining new life with recent browser updates. By collecting and summarizing CRLs for their users, browsers are making reliable revocation of certificates a reality, improving both security and privacy on the web.
Read more here : A New Life for Certificate Revocation Lists - Let's Encrypt (letsencrypt.org)