Why HTTP/2 Outperforms HTTP/1.1: Key Differences and Benefits

21CTO导读：HTTP/2 is the latest version of HTTP, soon to replace HTTP/1.1 after more than two decades of use.

Differences Between HTTP/2 and HTTP/1.1

HTTP/2 full name: HTTP/2.0, derived from Google’s SPDY protocol created in 2009.

Shortcomings of HTTP/1.1

The protocol was designed when web pages were tiny (<100 KB) and CSS did not exist.

Modern homepages can exceed 1.9 MB with over 100 objects that must be fetched before rendering.

HTTP/1.1 limits a client to two simultaneous connections per host; browsers now use 6‑8, but many sites still need dozens of TCP connections.

Only basic form validation and simple effects are possible; most interactivity requires JavaScript.

High bandwidth consumption and reliance on single Ajax requests make single‑page applications inefficient.

Features of HTTP/2.0

Uses binary data streams instead of inefficient text framing.

Header compression reduces overhead in request and response metadata.

Supports true pipelining, allowing asynchronous processing of multiple responses.

Multiplexing enables many streams over a single TCP connection, eliminating head‑of‑line blocking.

Server push lets the server proactively send resources the client is likely to need.

Illustration of multiplexing (train analogy):

Another diagram shows multiple streams sharing a single connection, similar to trains on one track.

In HTTP/1.x, connections must stay open for continuous data exchange, causing congestion and RTT waste; HTTP/2 allows each stream to be cut off and extracted independently.

Testing shows HTTP/2 can be up to ten times faster than HTTP/1.x when using HTTPS.

Adoption is growing: about 12% of the top 10 million websites already support HTTP/2, and all modern browsers (Firefox, Safari, Edge, Chrome, and other Blink‑based browsers) fully support it.

Author: 21CTO Community Compiled from: http://daniel.haxx.se/http2/