Tools

FormatJS's official localization review skill for software translators: read-only checks of UI strings and translations for ICU syntax, placeholders, terminology consistency and locale formats for dates, numbers and currency, listing issues with evidence and minimal fixes. Never edits files.

Open-source Simplified/Traditional Chinese converter: deterministic dictionary-based conversion (no LLM) covering variant characters and regional vocabulary for mainland China, Taiwan and Hong Kong, with limited Japanese kanji support. Runs offline; CLI plus Node.js and Python APIs.

Lingo.dev's official CLI: lingo push sends JSON, YAML, Markdown, PO, XLIFF, Android/Xcode strings and other files from your repo to its LLM localization engine, and lingo pull brings translations back; CI-ready. Needs a Lingo.dev account; usage-based pricing with a free sandbox.

Open-source, self-hostable localization platform with a built-in MCP server: agents search keys, create and edit translations, manage languages and run machine translation. Works with Tolgee Cloud or your own instance; create a project API key or personal access token in settings.

Agent skills maintained by the Flutter team: layered architecture, responsive layouts, fixing layout overflows, declarative routing, internationalization, JSON serialization, and widget and integration tests. Works alongside the Dart MCP server.

Translation management for Ruby/Rails: statically analyzes code to find missing and unused keys, normalizes locale files, fills gaps via Google Translate, DeepL or OpenAI, and exports CSV for translators. Requires the i18n gem (Rails default) and Bundler; machine translation needs an API key.

AI localization: deploy the server to your own Vercel account (Postgres and AI Gateway included; enable deployment protection afterwards), then run npx languine@selfhosted translate to translate locale files with LLMs. A GitHub Action can open PRs. Needs a Vercel account and Node.js.

Fixes spacing and full-width/half-width punctuation in mixed CJK and English text, understanding 28+ file types including Markdown, YAML and strings and comments in source code. Lint mode outputs a diff or JSON for CI checks on localized copy.

Sets up and audits i18n for React, Next.js and Vue apps: replaces hard-coded strings with message keys, checks that English and Chinese keys are complete and consistent, and verifies plurals and date and number formats, with a key audit script. Needs a local codebase and Python.

General Translation's gt CLI: a wizard sets up i18n for React, Next.js and similar apps, then sends UI strings and JSON, YAML or Markdown files for AI translation and writes them back, with CI support. Needs a Node.js project and a General Translation API key (free sign-up, usage-based pricing).

Open-source toolkit widely used in localization: converts between PO, XLIFF, TMX, CSV, subtitle and other translation formats, counts words, runs 40+ translation checks with pofilter and extracts frequent terms with poterminology. Needs Python 3.11+.

Intlayer's official MCP server: in projects using Intlayer, lets agents build dictionaries, fill in missing translations with AI, sync multilingual content with the Intlayer CMS and look up docs. Needs Node.js; AI translation needs your own LLM API key, CMS sync needs credentials.

Microsoft's official skill: has the agent use Microsoft Learn docs to call Azure text and document translation, enforce glossaries, train Custom Translator models and troubleshoot quotas and errors. For localization teams building batch translation; needs an Azure account and Translator resource.

Unbabel's machine-translation quality metric: comet-score rates translations per sentence and overall, XCOMET marks error spans and severity, and CometKiwi works without a reference. Good for spot-checking MT. Needs Python 3.8+; models download from Hugging Face, some need a license; GPU helps.

Offline translation sync for coding agents: hands only new strings in JSON, YAML, PO, CSV and other locale files to the agent for translation and never overwrites human-edited translations, saving tokens. Needs Node.js; calls no translation API itself.

Crowdin's official CLI: push source files and pull translations back in place, track progress, manage glossaries and TM, and run machine or AI pre-translation, with JSON output for agents. Needs a Crowdin account (free trial; free for open source) and a token; crowdin init sets up config.

i18next's official CLI: finds hard-coded strings in JS/TS code, extracts translation keys, checks which locales are missing entries and syncs locale files; init --yes sets up non-interactively, and a bundled agent skill guides app internationalization. Needs a Node.js project using i18next.

Lokalise's official CLI (lokalise2) covering the Lokalise API v2: upload and download language files and manage keys, translations, screenshots, translation tasks and contributors. Needs a Lokalise account (paid, 14-day free trial) and an API token passed via --token.

SimpleLocalize's official CLI: upload and download translation files, trigger machine and AI auto-translation, publish translations to the CDN, and extract translation keys from source code for CI. Needs a SimpleLocalize account and project API key; paid service with a 14-day free trial.

Locize's official CLI: sync local translation files with the Locize platform, add, remove and look up keys, download published translations, manage versions and branches, and export JSON, XLIFF, PO, CSV or Excel for translators. Needs a Locize account, project ID and API key; free plan available.

Phrase Strings' official CLI: phrase init walks you through config, then phrase push uploads language files and phrase pull fetches the latest translations; it also wraps the full API for projects, locales and keys. Needs a Phrase Strings account (paid, 14-day free trial) and an API token.

DeepL's official CLI: translate text and PDF, Word, PowerPoint and Excel documents while keeping formatting, with glossaries and translation memory. Needs a DeepL API key (free plan available); install from source with Node.js 24.15+. Have legal translations reviewed.

Official CLI for Weblate, the open-source translation platform: check translation progress for projects and components, upload and download translation files, lock components, and commit or push repository changes. Hosted or self-hosted; needs the server URL, an API key and Python.

Official CLI for Tolgee, the open-source localization platform: extract strings from code, push keys to Tolgee and pull the latest translations, and diff local files against the platform. Works with Tolgee Cloud or self-hosted; needs Node.js 18+ and a personal or project API key (tolgee login).