Cloudflare Plans a Free Public Certificate Authority With Post-Quantum Merkle Tree Certificates
On 29 September 2026 Cloudflare announced it intends to become a public certificate authority, issuing free classical TLS certificates and post-quantum Merkle Tree Certificates (MTCs) via ACME, only to clients that support ARI. Why post-quantum certificates need a new format, what's still pending (root programs, a GlobalSign root deal), and what it means for site owners.
On 29 September 2026, Cloudflare announced its intention to become a public certificate authority (CA) — issuing both ordinary TLS certificates and post-quantum Merkle Tree Certificates (MTCs) from one system, for free, via ACME. Nothing is being issued yet. (What Is an SSL Certificate?)
Why post-quantum certificates need a new format
Future quantum computers threaten the signature algorithms that certificates rely on. New post-quantum signature algorithms exist, but their signatures are large — one standardised scheme's signatures run to about 2.4 KB, versus 64 bytes for the elliptic-curve signatures most sites use today. A TLS handshake carries several signatures, so naively swapping algorithms would add kilobytes to every new connection and slow the web down. (TLS Handshake Explained)
Merkle Tree Certificates tackle this by issuing certificates in batches organised as a Merkle tree. The batch is signed and publicly logged once; a browser verifies that a site's certificate is included in a trusted batch using a small proof, instead of checking a chain of big signatures. The format is still an IETF draft.
Key exchange is already post-quantum on much of the web; authentication (certificates) is the harder half. Cloudflare's dashboards now show customers which requests used post-quantum key exchange.
What's planned
- Free certificates via ACME, the same protocol Let's Encrypt uses. (How Automatic SSL Works)
- Issuance only to clients that support ARI (ACME Renewal Information, RFC 9773), so the CA can tell clients when to renew.
- Production MTC issuance targeted for Q1 2027.
- Transparency commitments: reproducible builds of the signing software, attestations for the hardware security modules holding the keys, and a public dashboard of issuance health and incidents.
What's still pending
- Browser trust. Cloudflare has applied to the Chrome, Apple, Microsoft and Mozilla root programs; those programs control the timeline for classical certificates.
- Compatibility with older devices. Cloudflare signed an agreement to acquire trusted root key material from GlobalSign so certificates work on older devices; the deal hadn't closed at announcement.
What it means for you
- Today: nothing changes. Keep using Let's Encrypt or your host's automatic HTTPS.
- Make sure your ACME client supports ARI. It's required for Cloudflare's planned CA, and it's how Let's Encrypt's shorter lifetimes are meant to be handled. (Let's Encrypt Moves to 64-Day Certificates)
- Expect more competition for free certificates — good for resilience, since many sites depend on a single free CA today.
Source: Cloudflare Birthday Week 2026 wrap-up · InfoQ coverage
EasySpawn handles certificates for your domains automatically, so whichever CA and format the web moves to, your app keeps serving HTTPS. See how it works or join the waitlist.
Related: What Is HTTPS? · Encryption at Rest vs in Transit · Mutual TLS · Cloudflare Birthday Week 2026
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