FormatJS

This repository is the home of FormatJS and related libraries.

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Development

See CONTRIBUTING.md for instructions.

Published Packages

Choose by application ecosystem. Registry names identify how to install a package; implementation language can differ. For example, @formatjs/cli is Rust-backed and distributed through npm.

Ecosystem	Distribution	Entry point
JavaScript / TypeScript	npm	React, Vue, Svelte, message formatting, Intl polyfills, build tools
Rust	crates.io	Message runtime, parsers, Intl cores
Python	PyPI	Rust-backed message runtime and parser bindings
Hermes / React Native	GitHub Releases	Native SDK with Rust libraries and C++/JSI installers

Intl APIs: npm and Rust

npm packages expose JavaScript APIs with TypeScript types. Rust crates expose native operations for Rust applications and host integrations. LocaleMatcher is a proposal ponyfill; the other rows implement standardized Intl APIs.

API	JavaScript / TypeScript (npm)	Rust (crates.io)
Collator	@formatjs/intl-collator	formatjs_intl_collator
DateTimeFormat	@formatjs/intl-datetimeformat	formatjs_intl_datetimeformat
DisplayNames	@formatjs/intl-displaynames	formatjs_intl_displaynames
DurationFormat	@formatjs/intl-durationformat	formatjs_intl_durationformat
getCanonicalLocales	@formatjs/intl-getcanonicallocales	formatjs_intl_getcanonicallocales
ListFormat	@formatjs/intl-listformat	formatjs_intl_listformat
Locale	@formatjs/intl-locale	formatjs_intl_locale
LocaleMatcher	@formatjs/intl-localematcher	formatjs_intl_localematcher
NumberFormat	@formatjs/intl-numberformat	formatjs_intl_numberformat
PluralRules	@formatjs/intl-pluralrules	formatjs_intl_pluralrules
RelativeTimeFormat	@formatjs/intl-relativetimeformat	formatjs_intl_relativetimeformat
Segmenter	@formatjs/intl-segmenter	formatjs_intl_segmenter
supportedValuesOf	@formatjs/intl-supportedvaluesof	formatjs_intl_supportedvaluesof

DateTimeFormat calendar add-ons are npm packages named @formatjs/intl-datetimeformat-calendar-*; see calendar installation. Rust calendar support is in formatjs_intl_datetimeformat_calendars.

JavaScript / TypeScript libraries and tools (npm)

Purpose	Packages
Application APIs	react-intl, vue-intl, @formatjs/svelte-intl, @formatjs/intl
ICU MessageFormat	intl-messageformat, @formatjs/icu-messageformat-parser, @formatjs/icu-skeleton-parser
CLI	@formatjs/cli, @formatjs/cli-lib
Build transforms	babel-plugin-formatjs, @formatjs/ts-transformer, @formatjs/unplugin
Linting and editing	eslint-plugin-formatjs, @formatjs/editor
Utilities	@formatjs/bigdecimal, @formatjs/fast-memoize, @formatjs/utils, @formatjs/ecma376

@formatjs/cli selects its @formatjs/cli-native-* platform package automatically. Package versions and licenses are listed on npm; changelogs live under packages/.

Rust libraries (crates.io)

Purpose	Crates
Application message runtime	formatjs_intl, formatjs_intl_macros
ICU MessageFormat runtime	formatjs_icu_messageformat
ICU parsers	formatjs_icu_messageformat_parser, formatjs_icu_skeleton_parser
Platform printf parsers	formatjs_apple_printf_parser, formatjs_java_printf_parser
Locale-data infrastructure	formatjs_intl_data, formatjs_intl_data_build
Hermes native archive	formatjs_intl_hermes

See Rust Intl crates for locale-data features and the application runtime for message catalogs. Standalone CLI binaries are also available in CLI releases.

Python bindings (PyPI)

Install package	Python import	Purpose
py_intl	intl	Application message runtime and catalogs
icu_messageformat	icu_messageformat	ICU MessageFormat runtime
icu_messageformat_parser	icu_messageformat_parser	ICU message parser
icu_skeleton_parser	icu_skeleton_parser	Number/date skeleton parser

Install with python -m pip install <package>. These wheels bind the Rust implementations; see the Python package READMEs.

Native Hermes SDK (GitHub Releases)

SDK releases ship prebuilt Rust libraries, public headers, C++/JSI adapters, JS installers, and checksums for Android, iOS/simulator, macOS, and Linux. Integrate the SDK into your native app, then install standard Intl APIs into its Hermes runtime. See installation and supported targets.

Big Thanks

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