Open Source TypeScript Localization (L10N) Software

Internationalize your web apps on the client & server. FormatJS is a modular collection of JavaScript libraries for internationalization that are focused on formatting numbers, dates, and strings for displaying to people. It includes a set of core libraries that build on the JavaScript Intl built-ins and industry-wide i18n standards, plus a set of integrations for common template and component libraries. For most web projects, internationalization happens in the template or view layer, so we've built integrations with React & Vue. FormatJS is aligned with: ECMAScript Internationalization API (ECMA-402), Unicode CLDR, and ICU Message syntax. By building on these industry standards, FormatJS leverages APIs in modern browsers and works with the message syntax used by professional translators. FormatJS has been tested in all the major browsers (IE11, Chrome, FF & Safari) on both desktop and mobile devices.

Angular library to translate texts, dates, and numbers. This library is for the localization of Angular apps. It allows, in addition to translation, to format dates and numbers through Internationalization API.

Internationalize your web apps on the client & server. Formats ICU Message strings with number, date, plural, and select placeholders to create localized messages. This package aims to provide a way for you to manage and format your JavaScript app's string messages into localized strings for people using your app. You can use this package in the browser and on the server via Node.js. A very common example is formatting messages that have numbers with plural labels. With this package you can make sure that the string is properly formatted for a person's locale.

​Languine is an AI-powered localization platform designed to automate and streamline the translation process for applications, ensuring seamless integration within development workflows. It offers intelligent, context-aware translations across over 100 languages, maintaining brand voice and tone consistency. It provides a command-line interface and continuous integration/continuous deployment integration, allowing developers to manage translations directly or automate them within existing pipelines. Languine supports various file formats, including JSON, YAML, Markdown, and more, catering to diverse project requirements. It also features fine-tuning options, enabling customization of translations to align with specific brand nuances. Additionally, Languine offers a GitHub Action for automating localization directly within GitHub, ensuring translations stay synchronized with every commit and deployment.

JavaScript library for internalization (i18n) of JavaScript projects, including React, Vue, Node.js, and Angular. Use it everywhere. Lingui.js provides the essential intl functionality that works in any JavaScript project, and offers components for leveraging React rendering. Manage the whole intl workflow using Lingui CLI. It extracts messages from source code, validates messages from translators, and checks that all messages are translated before shipping to production. Use React components inside localized messages without any limitations. Writing rich-text messages is as easy as writing JSX. For AI to do great translations for you, context is critical. Translating UI copy is difficult because it's usually a list of short strings without enough context. Lingui's localization formats allow developers to write descriptions of where and how your keys are used.

Modern javascript i18n localization library based on ES6 tagged templates and the good old GNU gettext. Just tag your strings to make them translatable. Use a simple ttag-cli tool for translation extraction. Can be easily integrated with almost any workflow as it uses the babel-plugin for string extraction. Can be easily used with the typescript. Allows you to place translations into the sources on a build step. Gettext is a simple localization format with a rich ecosystem. Ttag has support for plurals, contexts, translator comments, and much more.

Lingo.dev is an AI-powered localization platform designed to automate and streamline the translation process for web and mobile applications. It integrates seamlessly with development workflows, automating translations upon code commits to ensure high-quality results without manual intervention. The platform offers Git-native UI localization, enabling automated pull requests that keep translations synchronized within CI/CD pipelines. For dynamic and user-generated content, Lingo.dev provides real-time translation through its API and SDK, incorporating context awareness for accurate localization. Its composable infrastructure supports full-stack localization across product interfaces, marketing sites, automated emails, and dynamic content from the outset. Users can customize translations to reflect their brand's unique voice and industry-specific terminology, with advanced options suitable for scaling teams.

Elegant lightweight internationalization library. eo-locale inspired by react-intl. Most popular internationalization library in the React community. 1.9 kB gzipped size. It is very important to provide small client javascript bundles for the best user experience. Within eo-locale, you can format dates, numeric values, and plural values.

i1n is a localization platform for developers. A CLI pushes your translation keys and gets them back translated with AI, with variable protection and TypeScript type generation. Review and edit translations in the dashboard, mark them as manually approved, and get notified when source text changes make translations stale. Ships with an MCP server that connects to AI coding assistants (Cursor, Claude Code, Windsurf) so your agent can internationalize components directly from the IDE. Bridge Mode wraps existing i18next or next-intl setups with type safety, no migration needed. Open source CLI (MIT). Free tier is permanent.

sveltekit-i18n is a tiny library with no external dependencies, built for Svelte and SvelteKit. It glues @sveltekit-i18n/base and @sveltekit-i18n/parser-default together to provide you the most straightforward sveltekit-i18n solution.