Why Country and Language Codes Matter
Every internationalized application needs country and language identifiers. Address forms validate country codes. Locale strings (en-US, fr-CA, ja-JP) combine language and country. Payment systems validate billing country. Shipping APIs need ISO country codes. But there are multiple formats for the same country — knowing which one an API expects prevents validation errors and silent failures.
ISO 3166 Country Codes
Three formats for every country, all defined by ISO 3166:
- Alpha-2: Two-letter code — US, GB, DE, JP, IN, BR. The most widely used format. Used in top-level domains (.us, .uk, .de), locale strings (en-US), and most APIs.
- Alpha-3: Three-letter code — USA, GBR, DEU, JPN, IND, BRA. More human-readable. Used in passports, machine-readable travel documents, and some government systems.
- Numeric: Three-digit code — 840, 826, 276, 392, 356, 076. Language-independent (no alphabet bias). Used in UN statistics, customs declarations, and systems that don't use Latin script.
ISO 639 Language Codes
- Alpha-2 (ISO 639-1): Two-letter codes — en, fr, de, ja, zh. The standard for web and software i18n.
- Alpha-3 (ISO 639-2/B and 639-2/T): Three-letter codes — eng, fra, deu, jpn, zho. Two variants: B (bibliographic, e.g., "ger" for German) and T (terminological, e.g., "deu" for German). Most modern systems use T codes.
- ISO 639-3: Three-letter codes covering ~8,000 languages — includes historical, constructed, and extinct languages. Used in linguistic research and comprehensive language taxonomies.
Locale Strings (IETF BCP 47)
Combining language and country: en-US, fr-CA, zh-Hans-CN (Chinese, Simplified script, China). These follow IETF BCP 47, which uses ISO 639 language codes and ISO 3166 country codes with extensions for script and region variants.
Look Up Any Code
Use ToolsVito's Country & Language Codes reference — search any country or language and get the alpha-2, alpha-3, and numeric codes in every format. Copy instantly. All in your browser.