Why it matters
Common mistakes are country codes used as languages (se, dk and cz instead of sv, da and cs), wrong regions (UK instead of GB, SW instead of CH, GE instead of DE), regions that are not countries (EU, a city such as LA) and a region on its own (GB). Some mistakes are valid codes for something else (se is Northern Sami, GE is Georgia) and silently target the wrong audience.
How to meet it
Store each version as a language plus an optional script and region (sv-SE, de-CH, en-GB, zh-Hant, zh-Hans-CN), validate every value against the ISO 639-1, ISO 15924 and ISO 3166-1 Alpha-2 lists in a build check or crawler rule, and use x-default for everyone else. hreflang targets countries, not groups such as the EU.
How to test it
An automated check confirms every value matches x-default or language[-Script][-REGION] (case-insensitive), with each part checked against ISO 639-1, ISO 15924 and ISO 3166-1 Alpha-2.
How Regensbot covers it
Decided from one URL.
An audit reads the response, the headers, the HTML, robots.txt, the sitemaps and the structured data, and the finding shows the evidence it saw.
Sources
Google documents01
Claims in the knowledge base10
- D2-C575ConsistentFocusing on Internationalisation and LocalisationShown on screen
- D2-C576ConsistentFocusing on Internationalisation and LocalisationSaid on stage
- D2-C578ConsistentFocusing on Internationalisation and LocalisationSaid on stage
- D2-C579ConsistentFocusing on Internationalisation and LocalisationShown on screen
- D2-C580ConfirmedFocusing on Internationalisation and LocalisationShown on screen
- D2-C581ConsistentFocusing on Internationalisation and LocalisationShown on screen
- D2-C582ConfirmedFocusing on Internationalisation and LocalisationShown on screen
- D2-C583n/aFocusing on Internationalisation and LocalisationThe author's interpretation
- D2-C830SourceFocusing on Internationalisation and LocalisationGoogle's documentation
- D2-C962ConsistentFocusing on Internationalisation and LocalisationSaid on stage
Claim IDs refer to the Search Central Live 2026 knowledge base. The knowledge base (opens in a new tab)
- Confirmed
- Google's documentation states the same thing.
- Consistent
- Google's documentation supports it without stating it.
- Source
- The claim is the cited document itself.
- n/a
- Nothing to verify: a quotation, framing, opinion or analysis.