Let’s Encrypt will no longer include the “TLS Client Authentication” Extended Key Usage (EKU) in our certificates beginning in 2026. Most users who use Let’s Encrypt to secure websites won’t be affected and won’t need to take any action. However, if you use Let’s Encrypt certificates as client certificates to authenticate to a server, this change may impact you.
To minimize disruption, Let’s Encrypt will roll this change out in multiple stages, using ACME Profiles.
For the full details and schedule, please see our blog post.