TLS 1.2 vs TLS 1.3

TLS 1.3 is a major improvement over TLS 1.2, delivering faster handshakes, stronger security defaults, and a reduced attack surface. It was finalized in 2018 and is now the recommended standard for all new deployments.

Faster Handshakes

TLS 1.2 requires 2 round trips to establish a secure connection: one for key exchange negotiation and one for key exchange completion. TLS 1.3 reduces this to 1 round trip by combining these steps.

For resumed sessions, TLS 1.3 supports 0-RTT (zero round trip time) — the client sends encrypted application data with the very first flight. On a 100ms latency connection, this saves 100-200ms per new connection.

Stronger Security Defaults

TLS 1.3 removes all weak cipher suites, making misconfiguration nearly impossible. Only five cipher suites remain, all using AEAD (Authenticated Encryption with Associated Data) and ephemeral key exchange (forward secrecy).

TLS 1.2 supports over 300 cipher suites, many of which are insecure. Correctly configuring TLS 1.2 requires expertise to avoid weak algorithms.

Forward Secrecy

TLS 1.3 mandates forward secrecy — even if the server's private key is compromised in the future, past sessions cannot be decrypted. TLS 1.2 makes this optional; many configurations use RSA key exchange, which lacks forward secrecy.

Migration

Most modern servers support both TLS 1.2 and 1.3 simultaneously, allowing gradual migration. The recommendation is to enable TLS 1.3 as the preferred version while keeping TLS 1.2 as a fallback for older clients.

For more on security architecture, see our concepts library and system design interview guide. Explore pricing for practice.

The Bottom Line

TLS 1.3 should be enabled on every modern system. It is faster, simpler to configure correctly, and more secure than TLS 1.2. Keep TLS 1.2 as a fallback only for legacy client compatibility.