Skip to main content

Appendix D. Backward Compatibility

This appendix describes backward compatibility considerations for TLS 1.3.

D.1. Negotiating with an Older Server​

How TLS 1.3 clients negotiate with TLS 1.2 servers.

D.2. Negotiating with an Older Client​

How TLS 1.3 servers handle TLS 1.2 clients.

D.3. 0-RTT Backward Compatibility​

Considerations for 0-RTT with older protocol versions.

D.4. Middlebox Compatibility Mode​

How TLS 1.3 maintains compatibility with legacy middleboxes.

Security considerations when supporting older TLS versions.

Complete Compatibility Guidance: For complete backward compatibility specifications and recommendations, please refer to Appendix D of RFC 8446.