HTTP/3 is the third major version of the Hypertext Transfer Protocol (HTTP). This protocol is the foundation of data communication on the web.

Here are the key features of HTTP/3:

1. Core Protocol and Architecture

• QUIC Protocol: HTTP/3 is built on QUIC, a modern transport protocol that runs over UDP (User Datagram Protocol). This replaces the use of TCP (Transmission Control Protocol) found in its predecessors (HTTP/1.1 and HTTP/2).

• Enhanced Reliability: It replaces TCP’s three-way handshake with faster connection setups. QUIC uses 0-RTT and 1-RTT handshakes, which reduces delay and contributes to faster connection setup.

• RFC Standard: HTTP/3 is defined in RFC 9114.

2. Performance and Efficiency

• Elimination of HOL Blocking: HTTP/3 eliminates Head-of-Line (HOL) blocking at the transport layer. Unlike HTTP/2, if a packet is lost, it only affects individual streams, meaning delays in one part do not block the rest of the website.

• Faster Start Time: It provides a significantly faster start time, making website connections begin up to 80–90% faster than HTTP/2.

• Better Performance on Weak Networks: It offers better performance on mobile and high-latency networks. It handles bad or unstable internet connections more smoothly and can recover from lost data effectively.

• Connection Migration: HTTP/3 supports connection migration, which is particularly useful for users on mobile networks.

3. Security and Compatibility

• Built-in Encryption: It includes built-in encryption. TLS (Transport Layer Security) is mandatory and is integrated directly into QUIC, specifically using TLS 1.3.

• Modern Network Compatibility: HTTP/3 works well with modern networks because it uses UDP on port 443, which is already commonly used on the internet.

• Browser Support: It is already supported by major browsers including Chrome, Firefox, and Safari.

HTTP/3 acts like a modern multi-lane highway constructed specifically for data, where individual accidents (lost packets) affect only one lane, allowing the rest of the traffic (data streams) to continue moving rapidly, unlike previous protocols where a single accident could halt the entire road (HOL blocking).