HTTP/3 is the newest “version” of HTTP.

It builds on the foundations laid by HTTP/2 but introduces significant changes, primarily by shifting from TCP (Transmission Control Protocol) to QUIC (Quick UDP Internet Connections) as the underlying transport protocol.

This means that HTTP/3 will be based on a completely different tech stack compared to HTTP/2 and HTTP.

HTTP/3 offers several enhancements:

Reduced Latency: HTTP/3, by using QUIC, diminishes connection setup time. This means websites can load content quicker, especially noticeable on mobile networks or other high-latency environments.

Connection Resilience: With QUIC, if a user changes from one network to another (e.g., switching from Wi-Fi to 4G), the connection remains intact, leading to a smoother browsing experience.

Improved Congestion Control: QUIC has its congestion control mechanism, allowing for better data flow, especially in networks with packet loss.

Enhanced Security: While HTTP/2 encouraged the use of HTTPS, QUIC has built-in encryption, making browsing inherently more secure.

You can see the protocol version used by your website from the browser devtools, in the Network panel. h2 means HTTP/2 and h3 means HTTP/3:

Lessons in this unit:

0: Introduction
1: An HTTP request
2: HTTP Methods
3: HTTP Status Codes
4: HTTP Client/Server communication
5: HTTP Request Headers
6: HTTP Response Headers
8: HTTP/2
9: ▶︎ HTTP/3