The Internet Engineering Task Force has finalized RFC 9849, establishing the Encrypted ClientHello (ECH) standard for TLS 1.3. This new extension allows clients to encrypt the ClientHello message using the server's public key, protecting sensitive information like the Server Name Indication (SNI) from network observers.

ECH addresses a fundamental privacy gap in TLS 1.3, where the plaintext SNI field reveals the target domain during the initial handshake. The standard supports both shared mode, where a single provider terminates all connections, and split mode, where connections are relayed to backend servers. This flexibility enables deployment across various infrastructure topologies.

The specification includes comprehensive security considerations, covering everything from padding policies to active attack mitigations. While ECH doesn't solve all privacy concerns—DNS queries and IP addresses can still reveal server identity—it represents a significant step forward when combined with encrypted DNS mechanisms like DNS over HTTPS and TLS.