Knowledge base v2.13.0 · Community edition · data through 2 October 2026
Topic · Crawling
Google's crawlers use HTTP/1.1 and HTTP/2, not HTTP/3. Author’s view: serving HTTP/3 to browsers is fine as long as the older versions keep working. Day 1's second recording added the basics behind it: a URL states how a resource is requested (HTTP or HTTPS), where (the host) and what (the path), and DNS, the internet's address book, is consulted for each request to find the host's IP address.
What to do
Google's crawling talk opened with how the internet works (TCP/IP, internet service providers, IP addresses, URLs, DNS and HTTP), because crawling can only be understood with that wider scope.
Speaker Cherry PrommawinIn Day 1, 14:05 · How crawling worksEvidence transcript
A URL states how a resource is requested (the protocol, HTTP or HTTPS), where (the host, meaning which computer on the network) and what (the path to the exact page or file).
Speaker Cherry PrommawinIn Day 1, 14:05 · How crawling worksEvidence transcript
DNS works as the internet's address book: it is consulted for each request and tells the client at which IP address a host name can be reached.
Speaker Cherry PrommawinIn Day 1, 14:05 · How crawling worksEvidence transcript
Googlebot does not support HTTP/3 today.
In Day 1 · session not recordedEvidence notes
Used byrequirement DEV-SRV-07
Google's crawlers support HTTP/1.1 and HTTP/2, use whichever gives the best crawling performance, and may switch between sessions. HTTP/2 can save server resources but gives no ranking benefit.
Publisher GoogleAnnotates Day 1 · session not recorded
Used byrequirement DEV-SRV-07
Google's crawler overview says HTTP/1.1 is the default protocol of Google's crawlers and that a site can opt out of crawling over HTTP/2 by answering Google's HTTP/2 requests with a 421 status code.
Publisher GoogleAnnotates Day 1 · session not recorded
Used byrequirement DEV-SRV-07
This does not mean avoiding HTTP/3, which benefits browsers. The rule is never to run a host that only answers over HTTP/3, and to check that CDN or firewall rules written for HTTP/3 traffic do not break HTTP/1.1 and HTTP/2.
Author Ibrahim AnjroAnnotates Day 1 · session not recorded
Used byrequirement DEV-SRV-07
Opening Day 2, Google recapped that Day 1 began with how Search works and then covered crawling, including basics of how the internet works such as TCP/IP, so that attendees could understand how crawlers work.
Google's crawling talk opened with how the internet works (TCP/IP, internet service providers, IP addresses, URLs, DNS and HTTP), because crawling can only be understood with that wider scope.
Answer crawlers over HTTP/1.1 (HTTP/2 optional); never run a crawlable host on HTTP/3 only
Rests on 4 claims, 4 of them in this topic