Issue certificates
Cloudflare automatically issues certificates when you create a custom hostname.
For each custom hostname, Cloudflare issues two certificates bundled in chains that maximize browser compatibility (unless you upload custom certificates).
The primary certificate uses a P-256 key, is SHA-2/ECDSA signed, and will be presented to browsers that support elliptic curve cryptography (ECC). The secondary or fallback certificate uses an RSA 2048-bit key, is SHA-2/RSA signed, and will be presented to browsers that do not support ECC.
Refer to this certificate authorities reference page to learn more about the CAs that Cloudflare uses to issue SSL/TLS certificates.