TLS 1.3 cuts handshake to 1 round-trip. Click to see the flow.

What you're seeing

TLS 1.3 sends key share in the first ClientHello. Server responds with ServerHello + key share, certificate (encrypted with the derived handshake key), and Finished. The client sends Finished, and immediately can send encrypted application data — 1 round-trip total (vs 2 in TLS 1.2).

With session resumption, 0-RTT is possible: encrypted application data in the very first packet. Replayable, so only safe for idempotent operations.

★ KEY TAKEAWAY
TLS 1.3 cuts handshake to 1 RTT by sending key share in ClientHello. Drops 50% latency vs TLS 1.2.
▶ WHAT TO TRY
  • Click Run to watch each step.
  • 0-RTT resumption (not shown) can encrypt the first packet, at the cost of replay risk.
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