HTTP/2 is a major revision of the HTTP protocol that was published as RFC 7540 on 14 May 2015. According to Wikipedia, as of October 2021, 47% of the top 10 million websites supported HTTP/2.
HTTP2 was designed to bring significant improvement in efficiency, speed and security and is supported by most modern web browsers. Some of the improvements include:
- HTTP/2 is binary, instead of textual.
- It is fully multiplexed, sending multiple requests in parallel over a single TCP connection.
- It uses header compression HPACK to reduce overhead.
- It allows servers to “push” responses proactively into client caches instead of waiting for a new request for each resource
- It uses the new ALPN extension which allows for faster-encrypted connections since the application protocol is determined during the initial connection.
- It reduces additional round trip times (RTT), making your website load faster without any optimization.
There are a number of sites that provide tests to determine if a site supports HTTP/2. Here is one:
tools.keycdn.com/http2-test
On 17 September 2021 Google made the following announcement in the Google Search Central Blog:
Googlebot will soon speak HTTP/2
Google states there is no ranking benefit to a site being crawled using HTTP/2.
But that doesn't mean any performance benefits to a site from supporting HTTP/2 won't benefit a site's rank.
Michael