Regional Language Variants — en-US vs en-GB and Beyond

Regional Language Variants

The same language can vary significantly between regions. Regional subtags in BCP 47 help applications serve the right variant.

Major Regional Variants

English Variants

Tag	Region	Key Differences
en-US	United States	"color", "center", MM/DD/YYYY, $
en-GB	United Kingdom	"colour", "centre", DD/MM/YYYY, £
en-AU	Australia	"colour", DD/MM/YYYY, A$
en-CA	Canada	Mix of US/UK spelling, DD/MM/YYYY, C$
en-IN	India	UK spelling, lakhs/crores number system

Portuguese Variants

Tag	Region	Key Differences
pt-BR	Brazil	Different vocabulary, grammar, pronunciation
pt-PT	Portugal	European Portuguese, different spelling reform adoption

Spanish Variants

Tag	Region	Key Differences
es-ES	Spain	Vosotros form, European vocabulary
es-MX	Mexico	Ustedes form, Mexican vocabulary
es-AR	Argentina	Vos form, distinct pronunciation
es-419	Latin America	Generic Latin American Spanish

French Variants

Tag	Region	Key Differences
fr-FR	France	European French
fr-CA	Canada	Different vocabulary, pronunciation
fr-BE	Belgium	Different number words (septante, nonante)
fr-CH	Switzerland	Different number words (huitante)

What Changes Between Variants

1. Spelling: color/colour, organize/organise
2. Vocabulary: truck/lorry, elevator/lift
3. Date formats: MM/DD/YYYY vs DD/MM/YYYY
4. Number formats: 1,000.00 vs 1.000,00
5. Currency: symbol and position
6. Measurement units: imperial vs metric defaults
7. Grammar: different verb forms, formal/informal

When to Use Regional Variants

Use language-only (en, fr) when:

• Content does not have region-specific differences
• You have one version per language

Use language+region (en-US, fr-CA) when:

• Date, number, or currency formatting differs
• Spelling or vocabulary is region-specific
• Legal or regulatory content varies by country
• You have separate content teams per region

The Intl API and Regional Formatting

// Date formatting
new Intl.DateTimeFormat("en-US").format(date); // "2/28/2026"
new Intl.DateTimeFormat("en-GB").format(date); // "28/02/2026"

// Number formatting
new Intl.NumberFormat("de-DE").format(1234.5); // "1.234,5"
new Intl.NumberFormat("de-CH").format(1234.5); // "1’234.5"