Before a client can send its first HTTPS request, a TCP handshake plus a TLS 1.3 handshake cost blank round trips. QUIC (HTTP/3) combines them into blank.

Answer

Before a client can send its first HTTPS request, a TCP handshake plus a TLS 1.3 handshake cost 2 round trips. QUIC (HTTP/3) combines them into 1.

Also accepted: two for 2; one for 1.

Why

TLS 1.2 needed two round trips of its own, so three in total. With session resumption, TLS 1.3 and QUIC can even send data in the first flight (0-RTT), at the cost of replay risk for that data.

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