HTTP/1.1 vs HTTP/2 vs HTTP/3

The same page, three protocols. Watch head-of-line blocking move from the application, into TCP, and finally out of the way.

1.1: one response at a time

2: streams over TCP

3: streams over QUIC

Scenario

Animation Speed: 800ms per tick

Tick 0 · step 1 of 190/4 resources done

delivered to the pagearrived, waiting in a bufferlost, not yet resentretransmission

t=0The server is still working on style.css and app.js and logo.png and font.woff2; nothing else is ready to send.

Same Page, Three Protocols

HTTP/1.1loaded at t=36

HTTP/2loaded at t=18

HTTP/3loaded at t=18

Each bar is one resource's finish time. Real browsers soften HTTP/1.1 with up to six connections per host; QUIC also saves a round trip at setup by merging the transport and TLS handshakes.

Where the Blocking Lives

HTTP/1.1application: responses queue on a connection

HTTP/2transport: TCP delivers bytes in order

HTTP/3per stream only: QUIC orders each stream

Knowledge Check

Question 1 of 3

On a single HTTP/1.1 connection, the first response is slow to generate. What happens to the other resources?

DSAverse

HTTP/1.1 vs HTTP/2 vs HTTP/3

Same Page, Three Protocols

Where the Blocking Lives

Knowledge Check

See also

HTTP/1.1 vs HTTP/2 vs HTTP/3

Same Page, Three Protocols

Where the Blocking Lives

Knowledge Check

See also