HTTP/2.

HTTP/2 is the second major revision of the HTTP network protocol, standardised in 2015. Its key improvements over HTTP/1.1 address the protocol-level inefficiencies that cause web pages to load slowly: HTTP/1.1 can only process one request per TCP connection at a time (requiring multiple connections or 'request queuing'), while HTTP/2 allows multiplexing — multiple requests and responses simultaneously over a single connection.

HTTP/2 Features That Help Performance

Multiplexing eliminates the 'head-of-line blocking' problem where one slow asset delays all others. Header compression (HPACK) reduces the overhead of repetitive HTTP headers sent with every request. Server push allows the server to send assets the browser will need before it explicitly requests them (though this feature has seen limited real-world adoption). Binary framing makes the protocol more efficient for machines to parse than the text-based HTTP/1.1.

HTTP/2 and SEO

HTTP/2 is now supported by virtually all modern browsers and most web servers. Switching from HTTP/1.1 to HTTP/2 can improve page load speed, particularly for pages with many assets, which correlates with better Core Web Vitals scores. HTTP/2 requires HTTPS — so enabling HTTP/2 also implies enabling HTTPS, which is itself a ranking signal. HTTP/3 (based on QUIC protocol) is the next evolution, offering further improvements in connection establishment speed.