# Country code (ISO 3166-1)

Category: [International SEO](https://seo-geo-glossary.com/en/glossary/category/international-seo/) › [hreflang & language tags](https://seo-geo-glossary.com/en/glossary/category/international-seo/hreflang-language-tags/) · Also known as: ISO 3166-1

A **country code** under ISO 3166-1 is a standardized identifier for a country or territory. In everyday speech, "country code" can also mean a telephone dialing code (assessment). In SEO the ISO code matters, because it is the region part of hreflang values.

## Formats

ISO 3166-1 defines three formats. According to Wikipedia, the standard is maintained by the ISO 3166 Maintenance Agency and covers 249 assigned codes.

| Country | Alpha-2 | Alpha-3 | Numeric |
|---|---|---|---|
| Germany | DE | DEU | 276 |
| United Kingdom | GB | GBR | 826 |
| United States | US | USA | 840 |

The alpha-2 code is the one used in hreflang. Wikipedia notes that some codes are reserved on request, for example `UK` for the United Kingdom, while the assigned code is `GB`.

## Country codes in hreflang

Google's hreflang format takes a language code, followed by an optional region code in ISO 3166-1 Alpha 2 format. A region cannot stand alone. Google accepts upper and lower case and follows the ISO convention of uppercase region codes, as in `en-GB`. Reserved values such as `UK`, `EU` and `UN` are ignored.

## Example

```html
<link rel="alternate" hreflang="de-DE" href="https://example.com/de-de/" />
<link rel="alternate" hreflang="de-AT" href="https://example.com/de-at/" />
<link rel="alternate" hreflang="en-GB" href="https://example.com/en-gb/" />
```

## Common mistakes

- **Country code alone.** According to Google, specifying only the region (`DE`) is not valid. The value starts with the language code, such as `de-DE`.
- **Reserved codes.** `UK`, `EU` and `UN` have no effect in Google Search, says Google. The code for the United Kingdom is `GB`.
- **Regions outside the standards.** Google does not support codes such as `es-419` that are not listed in the standards.

## FAQ

**What is the ISO 3166 code for the USA?**
`US` as alpha-2, `USA` as alpha-3 and `840` as numeric code.

**Is UK a valid country code?**
Wikipedia lists `UK` as reserved on request of the United Kingdom, while the assigned code is `GB`. Google ignores `UK` in hreflang.

## Related terms

- [Language code (ISO 639-1)](https://seo-geo-glossary.com/en/glossary/language-code/index.md)
- [hreflang](https://seo-geo-glossary.com/en/glossary/hreflang/index.md)
- [ccTLD](https://seo-geo-glossary.com/en/glossary/cctld/index.md)
- [International SEO](https://seo-geo-glossary.com/en/glossary/international-seo/index.md)

## Sources

- [ISO 3166-1 – Wikipedia (secondary; iso.org returned HTTP 403)](https://en.wikipedia.org/wiki/ISO_3166-1)
- [ISO 3166 country codes – ISO](https://www.iso.org/iso-3166-country-codes.html)
- [Standard country or area codes for statistical use (M49) – United Nations Statistics Division](https://unstats.un.org/unsd/methodology/m49/overview/)
- [Tell Google about localized versions of your page – Google Search Central (updated 21.09.2026)](https://developers.google.com/search/docs/specialty/international/localized-versions)

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