Cloudflare attempts to provide compatibility for as wide a range of user agents (browsers, API clients, etc.) as possible. However, the specific set of supported clients can vary depending on the different SSL/TLS certificate types, your visitor’s , and the that issues the certificate.
Also, for zones on Free plan, Universal SSL is only compatible with browsers that support Elliptic Curve Digital Signature Algorithm (ECDSA).
Paid plans have additional compatibility, also supporting RSA algorithm.
Other certificate types
If your visitors use devices that have not been updated since 2011, they may not have SNI support.
To support non-SNI requests, you can: