HTTP/2 is the second major version of the HTTP protocol, standardized in RFC 9113 (the current revision, which replaces RFC 7540). It keeps the same request and response semantics as HTTP/1.1, such as methods, status codes and headers, and changes how they are transported.
How does HTTP/2 work?
- Binary framing: messages are split into binary frames instead of being sent as text.
- Multiplexing: many request and response exchanges share a single connection at the same time. HTTP/1.1 clients typically open several connections for this.
- Header compression: HTTP/2 compresses headers with HPACK, which reduces the repeated data in each request.
HTTP/2 runs over TCP. For HTTPS URLs, client and server agree on it during the TLS handshake through ALPN, using the identifier h2. A website owner does not change URLs or HTML for this; the web server or CDN enables the protocol.
| Version | Transport | Concurrent requests | Header fields | Use by Google's crawlers |
|---|---|---|---|---|
| HTTP/1.1 (RFC 9112) | TCP | no multiplexing layer; pipelining possible, responses come back in request order; often several TCP connections for parallel requests | whitespace-delimited text fields; often repetitive and verbose according to RFC 9113 | supported; Google's default version |
| HTTP/2 (RFC 9113) (this term) | TCP | yes, many requests interleaved on one connection; TCP-level packet loss still stalls all streams | binary frames, HPACK compression | supported since November 2020; no ranking boost; opt out with status code 421 |
| HTTP/3 (RFC 9114) | QUIC over UDP | yes, over independent QUIC streams; one blocked stream does not hold up the others | QPACK compression | not stated by Google; the crawler documentation lists only HTTP/1.1 and HTTP/2 |
All three versions carry the same HTTP semantics (methods, status codes, headers); they differ in how messages are transferred. Google's crawlers pick the version with the best crawling performance and may switch between crawling sessions. Google says HTTP/2 may save computing resources on both sides. Server logs show which version a request used. Sources: RFC 9112: HTTP/1.1; RFC 9113: HTTP/2; RFC 9114: HTTP/3; RFC 9000: QUIC; Google Crawling Infrastructure: Overview of Google crawlers and fetchers (last updated 2026-06-12); Google Search Central Blog: Googlebot will soon speak HTTP/2 (2020-09-17). Last checked: .
HTTP/2 and crawlers
Google’s crawlers and fetchers support HTTP/1.1 and HTTP/2, and Google says they use the version that provides the best crawling performance. Google’s documentation describes HTTP/1.1 as the default and notes that HTTP/2 can save resources for both sides. Which version a crawler used for a request is visible in server logs.
HTTP/2 changes how files are delivered, not what a page contains. Its effect on loading speed depends on the site. Google’s documentation says crawling over HTTP/2 can save computing resources but gives no ranking boost in Google Search.
Example
Checking the protocol of a response with curl:
curl -sI --http2 https://example.com/ | head -1
HTTP/2 200
Sources
- RFC 9113: HTTP/2rfc-editor.org
- Overview of Google crawlers and fetchers – Google Search Centraldevelopers.google.com
Last updated: