i18next-cli 🚀

A unified, high-performance i18next CLI toolchain, powered by SWC.

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i18next-cli is a complete reimagining of the static analysis toolchain for the i18next ecosystem. It consolidates key extraction, type safety generation, locale syncing, linting, and cloud integrations into a single, cohesive, and blazing-fast CLI.

🚀 Try it Now - Zero Config!

You can get an instant analysis of your existing i18next project without any configuration. Just run this command in your repository's root directory:

npx i18next-cli status

Or find hardcoded strings:

npx i18next-cli lint

Why i18next-cli?

i18next-cli is built from the ground up to meet the demands of modern web development.

• 🚀 Performance: By leveraging a native Rust-based parser (SWC), it delivers orders-of-magnitude faster performance than JavaScript-based parsers.
• 🧠 Intelligence: A stateful, scope-aware analyzer correctly understands complex patterns like useTranslation('ns1', { keyPrefix: '...' }), getFixedT, and aliased t functions, minimizing the need for manual workarounds.
• ✅ Unified Workflow: One tool, one configuration file, one integrated workflow. It replaces various syncing scripts.
• 🔌 Extensibility: A modern plugin architecture allows the tool to adapt to any framework or custom workflow.
• 🧑‍💻 Developer Experience: A fully-typed configuration file, live --watch modes, CLI output, and a migration from legacy tools.

Features

• Key Extraction: Extract translation keys from JavaScript/TypeScript files with advanced AST analysis.
• Type Safety: Generate TypeScript definitions for full autocomplete and type safety.
• Locale Synchronization: Keep all language files in sync with your primary language.
• Accurate Code Linting: Detect hardcoded strings with high precision and configurable rules.
• Translation Status: Get a high-level overview or a detailed, key-by-key report of your project's translation completeness.
• Plugin System: Extensible architecture for custom extraction patterns and file types (e.g., HTML, Handlebars).
• Legacy Migration: Automatic migration from i18next-parser configurations.
• Cloud Integration: Seamless integration with the locize translation management platform.

Installation

npm install --save-dev i18next-cli

Quick Start

1. Initialize Configuration

Create a configuration interactively:

npx i18next-cli init

Or manually create i18next.config.ts in your project root:

import { defineConfig } from 'i18next-cli';

export default defineConfig({
  locales: ['en', 'de'],
  extract: {
    input: ['src/**/*.{js,jsx,ts,tsx}'],
    output: 'public/locales/{{language}}/{{namespace}}.json',
  },
});

2. Check your Translation Status

Get an overview of your project's localization health:

npx i18next-cli status

3. Extract Translation Keys

npx i18next-cli extract

4. Generate Types (Optional)

npx i18next-cli types

Commands

init

Interactive setup wizard to create your configuration file.

npx i18next-cli init

extract

Parses source files, extracts keys, and updates your JSON translation files.

npx i18next-cli extract [options]

Options:

• --watch, -w: Re-run automatically when files change
• --ci: Exit with non-zero status if any files are updated (for CI/CD)
• --dry-run: Does not change any files - useful in combination with --ci (for CI/CD)
• --sync-primary: Sync primary language values with default values from code

Examples:

# One-time extraction
npx i18next-cli extract

# Watch mode for development
npx i18next-cli extract --watch

# CI mode (fails if files changed)
npx i18next-cli extract --ci

# Sync primary language with code defaults
npx i18next-cli extract --sync-primary

# Combine options for optimal development workflow
npx i18next-cli extract --sync-primary --watch

status [locale]

Displays a health check of your project's translation status. Can run without a config file.

Options:

• --namespace <ns>, -n <ns>: Filter the report by a specific namespace.

Usage Examples:

# Get a high-level summary for all locales and namespaces
npx i18next-cli status

# Get a detailed, key-by-key report for the 'de' locale
npx i18next-cli status de

# Get a summary for only the 'common' namespace across all locales
npx i18next-cli status --namespace common

# Get a detailed report for the 'de' locale, showing only the 'common' namespace
npx i18next-cli status de --namespace common

The detailed view provides a rich, at-a-glance summary for each namespace, followed by a list of every key and its translation status.

Example Output (npx i18next-cli status de):

Key Status for "de":

Overall: [■■■■■■■■■■■■■■■■■■■■] 100% (12/12)

Namespace: common
Namespace Progress: [■■■■■■■■■■■■■■■■■■■■] 100% (4/4)
  ✓ button.save
  ✓ button.cancel
  ✓ greeting
  ✓ farewell

Namespace: translation
Namespace Progress: [■■■■■■■■■■■■■■■■□□□□] 80% (8/10)
  ✓ app.title
  ✓ app.welcome
  ✗ app.description
  ...

types

Generates TypeScript definitions from your translation files for full type-safety and autocompletion.

npx i18next-cli types [options]

Options:

• --watch, -w: Re-run automatically when translation files change

sync

Synchronizes secondary language files against your primary language file, adding missing keys and removing extraneous ones.

npx i18next-cli sync

lint

Analyzes your source code for internationalization issues like hardcoded strings. Can run without a config file.

npx i18next-cli lint

migrate-config

Automatically migrates a legacy i18next-parser.config.js file to the new i18next.config.ts format.

npx i18next-cli migrate-config

# Using custom path for old config
npx i18next-cli migrate-config i18next-parser.config.mjs

Locize Integration

Prerequisites: The locize commands require locize-cli to be installed:

# Install globally (recommended)
npm install -g locize-cli

Sync translations with the Locize translation management platform:

# Download translations from Locize
npx i18next-cli locize-download

# Upload/sync translations to Locize  
npx i18next-cli locize-sync

# Migrate local translations to Locize
npx i18next-cli locize-migrate

Locize Command Options:

The locize-sync command supports additional options:

npx i18next-cli locize-sync [options]

Options:

• --update-values: Update values of existing translations on locize
• --src-lng-only: Check for changes in source language only
• --compare-mtime: Compare modification times when syncing
• --dry-run: Run the command without making any changes

Interactive Setup: If your locize credentials are missing or invalid, the toolkit will guide you through an interactive setup process to configure your Project ID, API Key, and version.

Configuration

The configuration file supports both TypeScript (.ts) and JavaScript (.js) formats. Use the defineConfig helper for type safety and IntelliSense.

💡 No Installation Required? If you don't want to install i18next-cli as a dependency, you can skip the defineConfig helper and return a plain JavaScript object or JSON instead. The defineConfig function is purely for TypeScript support and doesn't affect functionality.

Basic Configuration

// i18next.config.ts
import { defineConfig } from 'i18next-cli';

export default defineConfig({
  locales: ['en', 'de', 'fr'],
  extract: {
    input: ['src/**/*.{ts,tsx,js,jsx}'],
    output: 'locales/{{language}}/{{namespace}}.json',
  },
});

Alternative without local installation:

// i18next.config.js
export default {
  locales: ['en', 'de', 'fr'],
  extract: {
    input: ['src/**/*.{ts,tsx,js,jsx}'],
    output: 'locales/{{language}}/{{namespace}}.json',
  },
};

Advanced Configuration

import { defineConfig } from 'i18next-cli';

export default defineConfig({
  locales: ['en', 'de', 'fr'],
  
  // Key extraction settings
  extract: {
    input: ['src/**/*.{ts,tsx}'],
    output: 'locales/{{language}}/{{namespace}}.json',

    /** Glob pattern(s) for files to ignore during extraction */
    ignore: ['node_modules/**'],

    // Use '.ts' files with `export default` instead of '.json'
    outputFormat: 'ts',

    // Combine all namespaces into a single file per language (e.g., locales/en.ts)
    // Note: `output` path must not contain `{{namespace}}` when this is true.
    mergeNamespaces: false, 
    
    // Translation functions to detect. Defaults to ['t', '*.t'].
    // Supports wildcards for suffixes.
    functions: ['t', '*.t', 'i18next.t'],
    
    // React components to analyze
    transComponents: ['Trans', 'Translation'],
    
    // HTML tags to preserve in Trans component default values
    transKeepBasicHtmlNodesFor: ['br', 'strong', 'i', 'p'],
    
    // Hook-like functions that return a t function.
    // Supports strings for default behavior or objects for custom argument positions.
    useTranslationNames: [
      'useTranslation', // Standard hook (ns: arg 0, keyPrefix: arg 1)
      'getT',
      'useT',
      {
        name: 'loadPageTranslations',
        nsArg: 1,       // Namespace is the 2nd argument (index 1)
        keyPrefixArg: 2 // Options with keyPrefix is the 3rd (index 2)
      }
    ],

    // Add custom JSX attributes to ignore during linting
    ignoredAttributes: ['data-testid', 'aria-label'],

    // JSX tag names whose content should be ignored when linting
    ignoredTags: ['pre'],
    
    // Namespace and key configuration
    defaultNS: 'translation',
    nsSeparator: ':',
    keySeparator: '.', // Or `false` to disable nesting and use flat keys
    contextSeparator: '_',
    pluralSeparator: '_',
    
    // Preserve dynamic keys matching patterns
    preservePatterns: [
      'dynamic.feature.*',
      'generated.*.key'
    ],
    
    // Output formatting
    sort: true, // can be also a sort function => i.e. (a, b) => a.key > b.key ? -1 : a.key < b.key ? 1 : 0, // sort in reverse order
    indentation: 2, // can be also a string
    
    // Primary language settings
    primaryLanguage: 'en', // Defaults to the first locale in the `locales` array
    secondaryLanguages: ['de', 'fr'], // Defaults to all locales except primaryLanguage

    // Default value for missing keys in secondary languages
    // Can be a string, function, or object for flexible fallback strategies
    defaultValue: '', // Simple string: all missing keys get this value
    
    // Or use a function for dynamic defaults:
    // defaultValue: (key, namespace, language) => key, // i18next-parser style: use key as value
    // defaultValue: (key, namespace, language) => `TODO: translate ${key}`, // Mark untranslated keys
    // defaultValue: (key, namespace, language) => language === 'de' ? 'German TODO' : 'TODO', // Language-specific

    /** If true, keys that are not found in the source code will be removed from translation files. (default: true) */
    removeUnusedKeys: true,

    // Control whether base plural forms are generated when context is present
    // When false, t('key', { context: 'male', count: 1 }) will only generate 
    // key_male_one, key_male_other but NOT key_one, key_other
    generateBasePluralForms: true, // Default: true

    // Completely disable plural generation, even when count is present
    // When true, t('key', { count: 1 }) will only generate 'key' (no _one, _other suffixes)
    // The count option can still be used for {{count}} interpolation in the translation value
    disablePlurals: false, // Default: false
  },
  
  // TypeScript type generation
  types: {
    input: ['locales/en/*.json'],
    output: 'src/types/i18next.d.ts',
    resourcesFile: 'src/types/resources.d.ts',
    enableSelector: true, // Enable type-safe key selection
  },
  
  // Locize integration
  locize: {
    projectId: 'your-project-id',
    apiKey: process.env.LOCIZE_API_KEY, // Recommended: use environment variables
    version: 'latest',
  },
  
  // Plugin system
  plugins: [
    // Add custom plugins here
  ],
});

Advanced Features

Plugin System

Create custom plugins to extend the capabilities of i18next-cli. The plugin system provides several hooks that allow you to tap into different stages of the extraction process, with full access to the AST parsing context and variable scope information.

Available Hooks:

• setup: Runs once when the CLI is initialized. Use it for any setup tasks.
• onLoad: Runs for each file before it is parsed. You can use this to transform code (e.g., transpile a custom language to JavaScript).
• onVisitNode: Runs for every node in the Abstract Syntax Tree (AST) of a parsed JavaScript/TypeScript file. This provides access to the full parsing context, including variable scope and TypeScript-specific syntax like satisfies and as operators.
• extractKeysFromExpression: Runs for specific expressions during AST traversal to extract additional translation keys. This is ideal for handling custom syntax patterns or complex key generation logic without managing pluralization manually.
• extractContextFromExpression: Runs for specific expressions to extract context values that can't be statically analyzed. Useful for dynamic context patterns or custom context resolution logic.
• onEnd: Runs after all JS/TS files have been parsed but before the final keys are compared with existing translation files. This is the ideal hook for parsing non-JavaScript files (like .html, .vue, or .svelte) and adding their keys to the collection.
• afterSync: Runs after the extractor has compared the found keys with your translation files and generated the final results. This is perfect for post-processing tasks, like generating a report of newly added keys.

Basic Plugin Example:

import { glob } from 'glob';
import { readFile, writeFile } from 'node:fs/promises';

export const myCustomPlugin = () => ({
  name: 'my-custom-plugin',
  
  // Handle custom file formats
  async onEnd(keys) {
    // Extract keys from .vue files
    const vueFiles = await glob('src/**/*.vue');
    for (const file of vueFiles) {
      const content = await readFile(file, 'utf-8');
      const keyMatches = content.matchAll(/\{\{\s*\$t\(['"]([^'"]+)['"]\)/g);
      for (const match of keyMatches) {
        keys.set(`translation:${match[1]}`, {
          key: match[1],
          defaultValue: match[1],
          ns: 'translation'
        });
      }
    }
  }
});

Advanced Plugin with Expression Parsing:

export const advancedExtractionPlugin = () => ({
  name: 'advanced-extraction-plugin',
  
  // Extract keys from TypeScript satisfies expressions
  extractKeysFromExpression: (expression, config, logger) => {
    const keys = [];
    
    // Handle template literals with variable substitutions
    if (expression.type === 'TemplateLiteral') {
      // Extract pattern: `user.${role}.permission`
      const parts = expression.quasis.map(q => q.cooked);
      const variables = expression.expressions.map(e => 
        e.type === 'Identifier' ? e.value : 'dynamic'
      );
      
      if (variables.includes('role')) {
        // Generate keys for known roles
        keys.push('user.admin.permission', 'user.manager.permission', 'user.employee.permission');
      }
    }
    
    // Handle TypeScript satisfies expressions
    if (expression.type === 'TsAsExpression' && 
        expression.typeAnnotation?.type === 'TsUnionType') {
      const unionTypes = expression.typeAnnotation.types;
      for (const unionType of unionTypes) {
        if (unionType.type === 'TsLiteralType' && 
            unionType.literal?.type === 'StringLiteral') {
          keys.push(`dynamic.${unionType.literal.value}.extracted`);
        }
      }
    }
    
    return keys;
  },
  
  // Extract context from conditional expressions
  extractContextFromExpression: (expression, config, logger) => {
    const contexts = [];
    
    // Handle ternary operators: isAdmin ? 'admin' : 'user'
    if (expression.type === 'ConditionalExpression') {
      if (expression.consequent.type === 'StringLiteral') {
        contexts.push(expression.consequent.value);
      }
      if (expression.alternate.type === 'StringLiteral') {
        contexts.push(expression.alternate.value);
      }
    }
    
    // Handle template literals: `${role}.${level}`
    if (expression.type === 'TemplateLiteral') {
      const parts = expression.expressions.map(expr =>
        expr.type === 'Identifier' ? expr.value : 'unknown'
      );
      if (parts.length > 0) {
        const joins = expression.quasis.map(quasi => quasi.cooked);
        contexts.push(joins.reduce((acc, join, i) => 
          acc + (join || '') + (parts[i] || ''), ''
        ));
      }
    }
    
    return contexts;
  },
  
  // Handle complex AST patterns
  onVisitNode: (node, context) => {
    // Custom extraction for specific component patterns
    if (node.type === 'JSXElement' && 
        node.opening.name.type === 'Identifier' && 
        node.opening.name.value === 'CustomTransComponent') {
      
      const keyAttr = node.opening.attributes?.find(attr =>
        attr.type === 'JSXAttribute' && 
        attr.name.value === 'translationKey'
      );
      
      if (keyAttr?.value?.type === 'StringLiteral') {
        context.addKey({
          key: keyAttr.value.value,
          defaultValue: 'Custom component translation',
          ns: 'components'
        });
      }
    }
  }
});

Configuration:

import { defineConfig } from 'i18next-cli';
import { myCustomPlugin, advancedExtractionPlugin } from './my-plugins.mjs';

export default defineConfig({
  locales: ['en', 'de'],
  extract: {
    input: ['src/**/*.{ts,tsx,vue}'],
    output: 'locales/{{language}}/{{namespace}}.json'
  },
  plugins: [
    myCustomPlugin(),
    advancedExtractionPlugin()
  ]
});

Dynamic Key Preservation

Use preservePatterns to maintain dynamically generated keys:

// Code like this:
const key = `user.${role}.permission`;
t(key);

// With this config:
export default defineConfig({
  extract: {
    preservePatterns: ['user.*.permission']
  }
});

// Will preserve existing keys matching the pattern

Comment-Based Extraction

Extract keys from comments for documentation or edge cases:

// t('welcome.message', 'Welcome to our app!')
// t('user.greeting', { defaultValue: 'Hello!', ns: 'common' })

JavaScript & TypeScript Translation Files

For projects that prefer to keep everything in a single module type, you can configure the CLI to output JavaScript or TypeScript files instead of JSON.

Configuration (i18next.config.ts):

export default defineConfig({
  extract: {
    output: 'src/locales/{{language}}/{{namespace}}.ts', // Note the .ts extension
    outputFormat: 'ts', // Use TypeScript with ES Modules
  }
});

This will generate files like src/locales/en/translation.ts with the following content:

export default {
  "myKey": "My value"
} as const;

Merging Namespaces

You can also combine all namespaces into a single file per language. This is useful for reducing the number of network requests in some application setups.

Configuration (i18next.config.ts):

export default defineConfig({
  extract: {
    // Note: The `output` path no longer contains the {{namespace}} placeholder
    output: 'src/locales/{{language}}.ts',
    outputFormat: 'ts',
    mergeNamespaces: true,
  }
});

This will generate a single file per language, like src/locales/en.ts, with namespaces as top-level keys:

export default {
  "translation": {
    "key1": "Value 1"
  },
  "common": {
    "keyA": "Value A"
  }
} as const;

Migration from i18next-parser

Automatically migrate from legacy i18next-parser.config.js:

npx i18next-cli migrate-config

This will:

• Convert your existing configuration to the new format
• Map old options to new equivalents
• Preserve custom settings where possible
• Create a new i18next.config.ts file

Important: File Management Differences
Unlike i18next-parser, i18next-cli takes full ownership of translation files in the output directory. If you have manually managed translation files that should not be modified, place them in a separate directory or use different naming patterns to avoid conflicts.

CI/CD Integration

Use the --ci flag to fail builds when translations are outdated:

# GitHub Actions example
- name: Check translations
  run: npx i18next-cli extract --ci

Watch Mode

For development, use watch mode to automatically update translations:

npx i18next-cli extract --watch
npx i18next-cli lint --watch

Type Safety

Generate TypeScript definitions for full type safety:

// Generated types enable autocomplete and validation
t('user.profile.name'); // ✅ Valid key
t('invalid.key');       // ❌ TypeScript error

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Supported Patterns

The toolkit automatically detects these i18next usage patterns:

Function Calls

// Basic usage
t('key')
t('key', 'Default value')
t('key', { defaultValue: 'Default' })

// With namespaces
t('ns:key')
t('key', { ns: 'namespace' })

// With interpolation
t('key', { name: 'John' })

// With plurals and context
t('key', { count: 1 }); // Cardinal plural
t('keyWithContext', { context: 'male' });
t('keyWithDynContext', { context: isMale ? 'male' : 'female' });

// With ordinal plurals
t('place', { count: 1, ordinal: true });
t('place', {
  count: 2,
  ordinal: true,
  defaultValue_ordinal_one: '{{count}}st place',
  defaultValue_ordinal_two: '{{count}}nd place',
  defaultValue_ordinal_other: '{{count}}th place'
});

// With key fallbacks
t(['key.primary', 'key.fallback']);
t(['key.primary', 'key.fallback'], { defaultValue: 'The fallback value' });

// With structured content (returnObjects)
t('countries', { returnObjects: true });

The extractor correctly handles cardinal and ordinal plurals (count), as well as context options, generating all necessary suffixed keys (e.g., key_one, key_ordinal_one, keyWithContext_male). It can even statically analyze ternary expressions in the context option to extract all possible variations.

React Components

// Trans component
<Trans i18nKey="welcome">Welcome {{name}}</Trans>
<Trans ns="common">user.greeting</Trans>
<Trans count={num}>You have {{num}} message</Trans>
<Trans context={isMale ? 'male' : 'female'}>A friend</Trans>

// useTranslation hook
const { t } = useTranslation('namespace');
const { t } = useTranslation(['ns1', 'ns2']);

Complex Patterns

// Aliased functions
const translate = t;
translate('key');

// Destructured hooks
const { t: translate } = useTranslation();

// getFixedT
const fixedT = getFixedT('en', 'namespace');
fixedT('key');

Programmatic Usage

In addition to the CLI commands, i18next-cli can be used programmatically in your build scripts, Gulp tasks, or any Node.js application:

Basic Programmatic Usage

import { runExtractor, runLinter, runSyncer, runStatus, runTypesGenerator } from 'i18next-cli';
import type { I18nextToolkitConfig } from 'i18next-cli';

const config: I18nextToolkitConfig = {
  locales: ['en', 'de'],
  extract: {
    input: ['src/**/*.{ts,tsx,js,jsx}'],
    output: 'locales/{{language}}/{{namespace}}.json',
  },
};

// Run the complete extraction process
const wasUpdated = await runExtractor(config);
console.log('Files updated:', wasUpdated);

// Check translation status programmatically
await runStatus(config);

// Run linting
await runLinter(config);

// Sync translation files
await runSyncer(config);

// types generattion
await runTypesGenerator(config);

Build Tool Integration

Gulp Example:

import gulp from 'gulp';
import { runExtractor } from 'i18next-cli';

gulp.task('i18next-extract', async () => {
  const config = {
    locales: ['en', 'de', 'fr'],
    extract: {
      input: ['src/**/*.{ts,tsx,js,jsx}'],
      output: 'public/locales/{{language}}/{{namespace}}.json',
    },
  };
  
  await runExtractor(config);
});

Webpack Plugin Example:

class I18nextExtractionPlugin {
  apply(compiler) {
    compiler.hooks.afterEmit.tapAsync('I18nextExtractionPlugin', async (compilation, callback) => {
      await runExtractor(config);
      callback();
    });
  }
}

Available Functions

• runExtractor(config, options?) - Complete extraction with file writing
• runLinter(config) - Run linting analysis
• runSyncer(config) - Sync translation files
• runStatus(config, options?) - Get translation status
• runTypesGenerator(config) - Generate types

This programmatic API gives you the same power as the CLI but with full control over when and how it runs in your build process.

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Gold Sponsors

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From the creators of i18next: localization as a service - locize.com

A translation management system built around the i18next ecosystem - locize.com.

With using locize you directly support the future of i18next.

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