HTTP/3
The version of HTTP that runs over QUIC on UDP, removing transport-level head-of-line blocking and speeding up connection setup.
Technicalh2
HTTP/2
A binary, multiplexed version of HTTP that carries many concurrent requests over one TCP connection with header compression.
In full
Multiplexing removes the head-of-line blocking that made domain sharding and sprite sheets worthwhile under HTTP/1.1, so those old optimisations are now counterproductive. Googlebot crawls over HTTP/2 where the server supports it, which reduces connection overhead for both sides. HTTP/2 still suffers TCP-level head-of-line blocking on lossy networks, which is what HTTP/3 addresses.
Example
Consolidating assets that were split across four sharded subdomains onto one HTTP/2 origin reduces handshakes and improves TTFB.
Related terms
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Content Delivery Network
A distributed network of edge servers that caches and serves content close to users, reducing latency and offloading the origin.
Googlebot
Google's main web crawler, which fetches pages for Google Search using two user agents: Googlebot Smartphone and Googlebot Desktop.