In short. Google supports ISO 639-1 languages with optional ISO 3166-1 Alpha 2 regions, ISO 15924 scripts and x-default, while EU, UN and UK region codes have no effect.
Definition: As of 17 October 2026, Google's
hreflangannotations identify alternate page versions using an ISO 639-1 language code and an optional ISO 3166-1 Alpha 2 region code. Google also supports ISO 15924 script codes and the reservedx-defaultfallback value.
Key facts
- Google's localized versions documentation requires a language code first; a region code alone is invalid.
- The Library of Congress language code list identifies ISO 639-1 as the alpha-2 code system and lists
befor Belarusian. - Unicode's ISO 15924 script code list identifies
Hansas the simplified Han script variant andHantas the traditional variant.
Which language and region combinations does Google support?
Google's supported codes guidance describes a language code followed, optionally, by a hyphen and a region code. Its examples include de for German content independent of region, en-GB for English content for users in the UK, and de-ES for German content for users in Spain.
For Belgium, the same guidance gives de-BE for German, nl-BE for Dutch, and fr-BE for French.
Google's HTML example includes the following annotations. These belong in the page's <head> element, and every alternate page carries the same set, including its own URL:
<link rel="alternate" hreflang="en-GB"
href="https://en-gb.example.com/page.html" />
<link rel="alternate" hreflang="en-US"
href="https://en-us.example.com/page.html" />
<link rel="alternate" hreflang="en"
href="https://en.example.com/page.html" />
<link rel="alternate" hreflang="de"
href="https://de.example.com/page.html" />
<link rel="alternate" hreflang="x-default"
href="https://www.example.com/" />
Here, en identifies a generic English version, while en-GB and en-US identify regional English versions.
Which region codes fail Google's requirements?
Google's troubleshooting guidance requires officially assigned ISO 3166-1 Alpha 2 region codes. It names EU, UN, and UK as reserved codes whose use has no effect on Google Search. Google says it ignores that part of the annotation. Its documented code for English content targeting UK users is en-GB.
The same documentation explicitly identifies es-419 as unsupported because its region code falls outside the supported standard.
A bare be has a different problem when intended to target Belgium: the first code means Belarusian. Google does not automatically derive a language from a country code. Its Belgian examples pair the language with BE, as in fr-BE.
How do script codes and x-default fit?
A script code identifies a writing system or script variant. Google's script examples include zh-Hant for Traditional Chinese and zh-Hans for Simplified Chinese. A region can follow the script: zh-Hans-US specifies Simplified Chinese for users in the United States. With zh-TW, Google derives the Traditional Chinese script from the region.
The reserved value x-default identifies the fallback page when no other language or region annotation matches the user's browser setting. The same documentation recommends it for language selector pages and uses it without an additional language code.
Related terms
- hreflang
- How do I list language alternatives in an XML sitemap?
- How do I check reciprocal hreflang links between translations?
- How do I mark a language selector page with x-default?
FAQ
Must I write region codes in uppercase?
Google's code guidance says hreflang values are case-insensitive. Uppercase region codes, such as en-GB, follow the ISO convention.
Can I use a language code without a country?
Yes. The same documentation gives de for German content independent of region and recommends a generic en page alongside regional English alternatives.
Does hreflang tell Google what language my page contains?
Google's documentation says it determines page language with algorithms. It uses hreflang to understand that pages are localized variations of the same content.
Sources
- Google Search Central, "Tell Google about localized versions of your page", updated 21 September 2026
- Library of Congress, "Codes for the Representation of Names of Languages", codes updated 15 January 2026
- Unicode, "ISO 15924 Alphabetical Code List", undated
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