For a general-purpose country identifier, start with ISO 3166-1 alpha-2—but confirm the format and accepted values required by the system receiving your data. “Country code” can also mean a telephone calling code, currency code, subdivision identifier, or a private label; these are different schemes and are not interchangeable.
What are country codes?
ISO 3166 is the international standard for representing country and subdivision names in code form. Its parts cover different needs: ISO 3166-1 covers current country names, ISO 3166-2 covers subdivisions, and ISO 3166-3 covers formerly used country names. Choose the part that matches your data rather than treating every identifier as one universal list. ISO’s overview of country codes explains the standard’s scope.
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Country identifiers are also distinct from telephone calling codes, currency codes, language codes, and labels created for an individual system. Each has its own purpose and maintenance process.
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How do I choose between alpha-2, alpha-3, and numeric-3?
| Format | What it looks like | When to use it |
|---|---|---|
| Alpha-2 | Two letters | ISO recommends this as the general-purpose country-code format. Use it when the receiving schema expects it. |
| Alpha-3 | Three letters | Use it when a specification requires it or when its closer association with the country name is useful. It is not an automatic substitute for alpha-2. |
| Numeric-3 | Three digits | Useful where Latin script should be avoided. Preserve the value as a code or string if formatting or leading zeroes could otherwise be lost. |
These formats identify countries, not every place or area a particular application might accept. An API may define a narrower set than the ISO standard, so check the endpoint’s documented enum and version.
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When do subdivisions and historical names matter?
Subdivisions
ISO 3166-2 codes identify subdivisions such as states or provinces. A code combines the country’s alpha-2 element with up to three additional characters. Subdivision names and codes may rely on official national sources, so confirm the relevant list when building address or regional data.
Formerly used country names
ISO 3166-3 covers formerly used country names. Include historical identifiers when you need to read or preserve legacy records; a current-country dropdown usually has a different scope.
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Who assigns official country codes?
After notification by the United Nations, the ISO 3166 Maintenance Agency assigns alpha-2 and alpha-3 code elements to new UN member states. The UN assigns numeric codes. ISO generally does not assign official country codes to geopolitical areas or countries that are not UN members, though dependencies of UN member states may be considered under established criteria. ISO’s country-code overview describes the standard and its assignment framework.
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ISO also documents reserved and user-assigned ranges. A value chosen by one user is not necessarily compatible with another organization’s value; ISO does not provide a shared meaning for such locally assigned codes. If your system needs a private code, document its owner and mapping, and do not present it as globally standardized.
Where can I get an official, current list?
Use ISO’s Online Browsing Platform to consult official entries, or see the Country Codes Collection information. ISO says the codes may be used free of charge. Its paid collection offers official lists for countries, subdivisions, and formerly used codes in XML, CSV, and XLS, with notifications when changes are made.
The standard record identifies ISO 3166-1:2020 as the fourth edition, published in August 2020 and confirmed current in 2025. That edition record does not mean the code list is frozen: maintenance updates can occur. Distinguish the standard’s edition from the ongoing maintenance of its entries. ISO’s record for ISO 3166-1:2020 gives its publication and confirmation details.
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Are telephone calling codes the same as ISO country codes?
No. Telephone calling codes and the phone-number metadata used to interpret numbers belong to a separate system. A current telephone library release is not evidence that ISO 3166 identifiers changed.
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For example, Google libphonenumber’s v9.0.40 release, dated September 23, 2026, reports phone-number metadata changes for several region codes, as well as geocoding and carrier-data changes. That is a dated update to the library’s phone data, not a revision to ISO country identifiers. Check the v9.0.40 release notes when implementing against that version.
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Why date country-code examples and data sources?
Related datasets can change independently. REST Countries’ September 2026 changelog reports that Zimbabwe’s currency data now lists Zimbabwe Gold (ZWG) in place of the retired Zimbabwean dollar (ZWL), and Curaçao and Sint Maarten list the Caribbean guilder (XCG) in place of the Netherlands Antillean guilder (ANG). These are currency-data updates, not ISO country-code changes. The changelog also notes additions or corrections to descriptions and flag descriptions. See the REST Countries API documentation and changelog for the dated entries.
Platform APIs can also adopt fields on their own version schedules. Shopify’s Customer Account API version 2026-10 adds countryCode to customer address inputs and objects, using ISO 3166-1 alpha-2 values. In that version, territoryCode is deprecated but remains supported. The September 8, 2026 changelog says versions 2026-07 and earlier are unchanged, and no removal version had been announced. This guidance applies to that API and version, not to every Shopify API. See Shopify’s changelog entry.
Quick Recap
How to build a reliable country-code feature
- Read the receiving system’s contract. Confirm which ISO part and format it accepts, which areas it includes, and which API version applies. An API-specific enum may be narrower than the full standard.
- Store identifiers separately from display names. Keep the code value stable and store or generate localized country names independently. A translated label should not replace the identifier.
- Set the feature’s scope. Decide whether you need only current country entries, or also subdivisions and historical names.
- Validate against the right maintained source. Use ISO for official standard lists and the relevant provider’s current release for API, currency, or phone metadata.
- Govern private values explicitly. If local codes are necessary, document who owns them and how they map to standardized values. Do not assume another system will interpret them the same way.
- Record versions and dates. Keep the source, code family, and API or dataset version with implementation notes so future updates can be assessed without confusing one scheme’s changes for another’s.
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