# HTTP/2 and HTTP/3 — Web Performance Optimization

Source: https://www.skillbyai.com/en/web-performance/web-perf-07

> Modern protocols that improve performance through multiplexing, header compression, and faster handshakes.

## HTTP/2 multiplexing

HTTP/2 sends multiple requests over one connection simultaneously. No need to bundle assets or domain sharding. Header compression (HPACK) reduces overhead. Automatic prioritization of critical resources.

## HTTP/3 and QUIC

HTTP/3 uses QUIC (UDP-based) instead of TCP. Faster connection establishment (0-RTT resumption), better loss recovery. Particularly beneficial for high-latency and mobile networks.

## Protocol adoption timeline

HTTP/1.1 is legacy, HTTP/2 is supported by nearly all browsers, and HTTP/3 is growing but not universal. Check your server and CDN support. Most modern CDNs support both HTTP/2 and HTTP/3.

Quick check

**Quiz:** What is a key advantage of HTTP/3?

- [ ] Smaller file sizes
- [ ] No compression needed
- [ ] It requires a separate connection per request
- [x] Uses UDP instead of TCP for faster handshake

*Answer:* Uses UDP instead of TCP for faster handshake. HTTP/3 runs over QUIC (UDP), which speeds up connection setup and recovers from loss better.