HTTP/3 is the third major version of the Hypertext Transfer Protocol, standardised in RFC 9114 published in June 2022. Unlike HTTP/1.1 and HTTP/2, which run over TCP, HTTP/3 is built on QUIC — a multiplexed transport protocol that runs over UDP. The key advantage for web performance is that QUIC eliminates head-of-line blocking at the transport layer: in HTTP/2, a single dropped TCP packet stalls all streams sharing that connection, whereas in QUIC, streams are independent so packet loss only affects the stream it belongs to. HTTP/3 also reduces connection establishment time through a combined TLS 1.3 and QUIC handshake that typically completes in a single round trip (or zero round trips for repeat connections), directly improving Time to First Byte. Major CDNs including Cloudflare, Google, and Fastly deployed HTTP/3 support during 2020–2022. For SEO, HTTP/3 can measurably improve Core Web Vitals on high-latency or lossy connections. Googlebot supports HTTP/3 crawling.