# HTTP/2

Category: [Technical SEO](https://seo-geo-glossary.com/en/glossary/category/technical-seo/) › [Servers, HTTP & caching](https://seo-geo-glossary.com/en/glossary/category/technical-seo/servers-http-caching/) · Also known as: HTTP2

**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.

## 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:

```bash
curl -sI --http2 https://example.com/ | head -1
HTTP/2 200
```

## HTTP versions compared

| 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) | 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 |

Sources: [RFC 9112: HTTP/1.1](https://www.rfc-editor.org/rfc/rfc9112.html); [RFC 9113: HTTP/2](https://www.rfc-editor.org/rfc/rfc9113.html); [RFC 9114: HTTP/3](https://www.rfc-editor.org/rfc/rfc9114.html); [RFC 9000: QUIC](https://www.rfc-editor.org/rfc/rfc9000.html); [Google Crawling Infrastructure: Overview of Google crawlers and fetchers (last updated 2026-06-12)](https://developers.google.com/crawling/docs/crawlers-fetchers/overview-google-crawlers); [Google Search Central Blog: Googlebot will soon speak HTTP/2 (2020-09-17)](https://developers.google.com/search/blog/2020/09/googlebot-will-soon-speak-http2). Last checked: October 8, 2026

## Not to be confused with

- [HTTP/3](https://seo-geo-glossary.com/en/glossary/http-3/index.md): carries HTTP over QUIC, which is built on UDP, instead of over TCP. A lost packet delays only the affected stream, not every stream on the connection. Google's documentation of its crawlers does not mention HTTP/3.

## Related terms

- [HTTP/3](https://seo-geo-glossary.com/en/glossary/http-3/index.md)
- [HTTP header](https://seo-geo-glossary.com/en/glossary/http-header/index.md)
- [HTTPS](https://seo-geo-glossary.com/en/glossary/https/index.md)
- [HTTP status code](https://seo-geo-glossary.com/en/glossary/http-status-code/index.md)
- [Page speed](https://seo-geo-glossary.com/en/glossary/page-speed/index.md)

## Sources

- [RFC 9113: HTTP/2](https://www.rfc-editor.org/rfc/rfc9113)
- [Overview of Google crawlers and fetchers – Google Search Central](https://developers.google.com/crawling/docs/crawlers-fetchers/overview-google-crawlers)

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Last updated: October 8, 2026
URL: https://seo-geo-glossary.com/en/glossary/http-2/