Let's Encrypt Announces Merkle Tree Certificates for Post-Quantum Web PKI (letsencrypt.org)

• Let's Encrypt to deploy Merkle Tree Certificates for post-quantum security
• Staging late 2026, production 2027
• MTCs reduce handshake size vs. ML-DSA
• IETF PLANTS standardizing; Chrome and Cloudflare testing
• Current certificates unchanged; gradual migration

"Let's Encrypt will adopt Merkle Tree Certificates (MTCs) to secure the Web PKI against quantum threats. Staging environment targeted for late 2026, production in 2027. MTCs dramatically reduce TLS handshake size compared to direct ML-DSA signatures. The IETF PLANTS working group is standardizing MTCs, with Chrome and Cloudflare already experimenting. Current certificates remain unaffected during the transition."