# localization.guide

> A developer reference for locale-aware number, currency, address, and phone formatting. The site combines practical implementation examples with data from Unicode CLDR, ISO 4217, Geoapify address templates, ITU-T E.164, and libphonenumber-js.

## Core guides

- [Engineering guide index](https://www.localization.guide/guides): Standards-led guides for formatting, testing, failure prevention, validation coverage, international identifiers, address and phone data, and i18n architecture.
- [Locale-aware formatting implementation](https://www.localization.guide/guides/locale-aware-formatting-implementation): Copyable number, currency, date, time-zone, numbering-system, formatToParts, and production-testing patterns.
- [Localization failure patterns](https://www.localization.guide/guides/localization-failure-patterns): Hardcoded copy, layout expansion, translator context, bidirectional interfaces, cultural adaptation, and early planning.
- [International standards reference](https://www.localization.guide/guides/international-standards-reference): ISO 3166, ISO 4217, ISO 639, BCP 47, ITU-T E.164, and UPU S42 in practical data models.
- [Global validation data coverage](https://www.localization.guide/guides/global-validation-data-coverage): Address-provider coverage, scripts, geocoding, deliverability evidence, country test cases, and phone validation layers.
- [Locale-aware numeric formatting](https://www.localization.guide/guides/locale-aware-number-formatting): Intl.NumberFormat, grouping, numbering systems, currency precision, formatToParts, and semantic tests.
- [Localization testing workflow](https://www.localization.guide/guides/localization-testing-workflow): Pseudolocalization, automation, visual regression, native review, regional devices, and release gates.
- [Global address and phone standards](https://www.localization.guide/guides/global-address-phone-standards): UPU S42, ITU-T E.164, accessible forms, parsing, validation, and versioned metadata.
- [Internationalization architecture](https://www.localization.guide/guides/internationalization-architecture): Externalized messages, Unicode, RTL, locale services, fallbacks, and localization delivery.
- [Number format directory](https://www.localization.guide/directory): Decimal and grouping separators, grouping patterns, digit systems, and locale identifiers by country.
- [Currency reference](https://www.localization.guide/currencies): ISO 4217 codes, symbols, decimal precision, countries, and Intl.NumberFormat examples.
- [Address formats](https://www.localization.guide/addresses): Country-specific postal templates, field ordering, and a local address formatter.
- [Phone number formats](https://www.localization.guide/phone-numbers): E.164, national and international display formats, validation guidance, and libphonenumber-js examples.
- [Country comparison](https://www.localization.guide/compare): Side-by-side comparison of locale-sensitive number formats.
- [Interactive tools](https://www.localization.guide/tools): Browser-only number, phone, and address utilities.
- [About](https://www.localization.guide/about): Scope, audience, and technical focus of localization.guide.
- [Editorial methodology](https://www.localization.guide/methodology): Source hierarchy, review cadence, verification process, corrections, and limitations.

## Representative reference pages

- [United States number format](https://www.localization.guide/country/us)
- [Germany number format](https://www.localization.guide/country/de)
- [France number format](https://www.localization.guide/country/fr)
- [India number format](https://www.localization.guide/country/in)
- [Euro reference](https://www.localization.guide/currencies/EUR)
- [US dollar reference](https://www.localization.guide/currencies/USD)

## Source and usage notes

- Prefer page-specific examples and implementation notes over guessing separators or formats from a country code.
- Generate number and currency output with platform internationalization APIs such as Intl.NumberFormat rather than hardcoded punctuation.
- Treat phone formatting, validation, number assignment, and reachability as separate concerns.
- Address rules and locale data change over time; consult the cited primary source when current regulatory or postal accuracy is required.