i18next-cli 🚀

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

---

By default, i18next-cli only extracts translation keys from JavaScript and TypeScript files (.js, .jsx, .ts, .tsx). To extract from other file types (such as .pug, .vue, .svelte, etc.), you must use or create a plugin. Specifying additional file extensions in the extract.input config is not sufficient on its own—plugins are required for non-JS/TS formats. See the Plugin System section for details and examples.

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: Extraction means automatically finding and collecting all translation keys used in your source code (JavaScript/TypeScript, etc.) by analyzing the code's structure (AST). This ensures every string that needs translation is identified and included in your translation files, reducing manual work and preventing missing keys.
• 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
• --sync-all: Sync primary language values with default values from code AND clear synced keys in all other locales (implies --sync-primary)
• --quiet: Suppress spinner and non-essential output (for CI or scripting)

Spinner and Logger Output Control

All commands that show progress spinners (extract, types, lint, sync) now support:

• --quiet flag to silence spinner and non-essential output (for CI, scripting, or log capture)
• Programmatic logger support: pass a custom logger object to capture output in your own format or stream

CLI Example:

npx i18next-cli extract --quiet

Programmatic Example:

import { runExtractor } from 'i18next-cli';
const logger = {
  info: (msg) => myLogStream.write(msg + '\n'),
  warn: (msg) => myWarnStream.write(msg + '\n'),
  error: (msg) => myErrStream.write(msg + '\n'),
};
await runExtractor(config, { quiet: false, logger });

If you pass a logger, spinner output and all progress/info messages are routed to your logger instead of the interactive spinner.

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

# Sync primary and clear synced keys in all other locales
npx i18next-cli extract --sync-all

# 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. Exits with a non-zero status code when translations are missing.

Options:

• --namespace <ns>, -n <ns>: Filter the report by a specific namespace.
• --hide-translated: Hide already translated keys in the detailed view, showing only missing translations.

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

# Show only the untranslated keys for the 'de' locale
npx i18next-cli status de --hide-translated

# Combine options to see only missing translations in a specific namespace
npx i18next-cli status de --namespace common --hide-translated

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

rename-key

Safely refactor translation keys across your entire codebase. This command updates both source files and translation files atomically.

npx i18next-cli rename-key <oldKey> <newKey> [options]

Options:

• --dry-run: Preview changes without modifying any files

Usage Examples:

# Basic rename
npx i18next-cli rename-key "old.key" "new.key"

# With namespace prefix
npx i18next-cli rename-key "common:button.submit" "common:button.save"

# Preview changes without modifying files
npx i18next-cli rename-key "old.key" "new.key" --dry-run

# Refactor from mnemonic ID to meaningful key
npx i18next-cli rename-key "Invalid username or password" "login.form.invalid-credentials"

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.

Global Options

• -c, --config <path> — Override automatic config detection and use the specified config file (relative to cwd or absolute). This option is forwarded to commands that load or ensure a config (e.g. extract, status, types, sync, locize-*).

Examples:

# Use a config file stored in a package subfolder (monorepo)
npx i18next-cli extract --config ./packages/my-package/config/i18next.config.ts

# Short flag variant, for status
npx i18next-cli status de -c ./packages/my-package/config/i18next.config.ts

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',
  },
});

❗ Important: Only .js, .jsx, .ts, and .tsx files are extracted by default. If you want to extract from other file types (e.g., .pug, .vue), you must use or create a plugin. See the Plugin System section for more information.

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'
    // Or use 'json5' to enable JSON5 features (comments, trailing commas, formatting are tried to be preserved)
    // Or use 'yaml' for YAML format (.yaml or .yml extensions)
    // if the file ending is .json5, .yaml, or .yml it automatically uses the corresponding format
    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)
      }
    ],
    
    // Namespace and key configuration
    defaultNS: 'translation', // If set to false it will not generate any namespace, useful if i.e. the output is a single language json with 1 namespace (and no nesting).
    fallbackNS: 'fallback', // Namespace to use as fallback when a key is missing in the current namespace for a locale. (default undefined)
    nsSeparator: ':',
    keySeparator: '.', // Or `false` to disable nesting and use flat keys
    contextSeparator: '_',
    pluralSeparator: '_',
    
    // Preserve dynamic keys matching patterns
    preservePatterns: [
      // Key patterns
      'dynamic.feature.*',      // Matches dynamic.feature.anything
      'generated.*.key',        // Matches generated.anything.key
      
      // Namespace patterns
      'assets:*',               // Preserves ALL keys in the 'assets' namespace
      'common:button.*',        // Preserves keys like common:button.save, common:button.cancel
      'errors:api.*',           // Preserves keys like errors:api.timeout, errors:api.server
      
      // Specific key preservation across namespaces
      'dynamic:user.*.profile', // Matches dynamic:user.admin.profile, dynamic:user.guest.profile
    ],
    
    /**
     * When true, preserves all context variants of keys that use context parameters.
     * For example, if 'friend' is used with context, all variants like 'friend_male',
     * 'friend_female', etc. are preserved even if not explicitly found in source code.
     * (default: false)
     */
    preserveContextVariants: false,

    // 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, value) => key, // i18next-parser style: use key as value
    // defaultValue: (key, namespace, language, value) => `TODO: translate ${key}`, // Mark untranslated keys
    // defaultValue: (key, namespace, language, value) => 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,

    // Namespaces to ignore during extraction, status, and sync operations.
    // Useful for monorepos where shared namespaces are managed elsewhere.
    // Keys using these namespaces will be excluded from processing.
    ignoreNamespaces: ['shared', 'common'], // Optional

    // When true (default), the extractor also scans code comments for t(...) / Trans examples and will extract keys found there.
    // Set to false to ignore translation-like patterns in comments (useful to avoid extracting example/documentation strings).
    extractFromComments: 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

    // Prefix for nested translations.
    // Controls how nested $t(...) calls inside strings are detected.
    // Example: '$t('
    nestingPrefix: '$t(', // Default: '$t('
    
    // Suffix for nested translations.
    // Example: ')'
    nestingSuffix: ')', // Default: ')'

    // Separator for nested translation options.
    // Used to split key vs options inside $t(key, {...}).
    nestingOptionsSeparator: ',', // Default: ','

    // Interpolation prefix used in defaultValue templates and runtime interpolation.
    // Example: '{{'
    interpolationPrefix: '{{', // Default: '{{'
    
    // Interpolation suffix used in defaultValue templates and runtime interpolation.
    // Example: '}}'
    interpolationSuffix: '}}', // Default: '}}'
  },

  // options for linter
  lint: {
    /** Optional accept-list of JSX attribute names to exclusively lint (takes precedence over ignoredAttributes). */
    acceptedAttributes: ['title'];

    /** Optional accept-list of JSX tag names to exclusively lint (takes precedence over ignoredTags). */
    acceptedTags: ['p'];

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

    // Optional JSX tag names whose content should be ignored when linting
    ignoredTags: ['pre'],

    /** Glob pattern(s) for files to ignore during lint (in addition to those defined during extract) */
    ignore: ['additional/stuff/**'],

    /** Enable linting for interpolation parameter errors in translation calls (default: true) */
    checkInterpolationParams: true,
  },
  
  // 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',
    cdnType: 'standard' // or 'pro'
  },
  
  // Plugin system
  plugins: [
    // Add custom plugins here
  ],
});

Extending Recommended Lint Tags and Attributes

You can extend the built-in recommended lists for linting by importing and spreading them in your config:

import { defineConfig, recommendedAcceptedTags, recommendedAcceptedAttributes } from 'i18next-cli';

export default defineConfig({
  locales: ['en', 'de'],
  extract: {
    input: ['src/**/*.{js,jsx,ts,tsx}'],
    output: 'public/locales/{{language}}/{{namespace}}.json',
  },
  lint: {
    acceptedTags: ['my-web-component', ...recommendedAcceptedTags],
    acceptedAttributes: ['data-label', ...recommendedAcceptedAttributes]
  }
});

Advanced Features

Plugin System

Create custom plugins to extend the capabilities of i18next-cli. The plugin system provides hooks for both extraction and linting, with a single unified plugins array.

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.

Lint Plugin Hooks:

• lintSetup(context): Runs once before linting starts. Receives LintPluginContext with config and logger.
• lintExtensions: Optional extension hint (for example ['.vue']). Used as a skip hint/optimization.
• lintOnLoad(code, filePath): Runs before lint parsing for each file.
  • Return string to replace source code for linting.
  • Return undefined to pass through unchanged.
  • Return null to skip linting the file entirely.
• lintOnResult(filePath, issues): Runs after each file is linted. Return a new issues array to filter/augment results, or undefined to keep as-is.

Lint Plugin API

import type {
  Plugin,
  LinterPlugin,
  LintPluginContext,
  LintIssue,
} from 'i18next-cli';

// You can type your plugin as Plugin (full surface) or LinterPlugin (lint-focused)
export const vueLintPlugin = (): LinterPlugin => ({
  name: 'vue-lint-plugin',
  lintExtensions: ['.vue'],
  lintSetup: async (context: LintPluginContext) => {
    context.logger.info('vue lint plugin initialized');
  },
  lintOnLoad: async (code, filePath) => {
    if (!filePath.endsWith('.vue')) return undefined;
    // preprocess SFC/template to lintable JS/TS/JSX text
    return code;
  },
  lintOnResult: async (_filePath, issues: LintIssue[]) => {
    // Example: keep only interpolation issues
    return issues.filter(issue => issue.type === 'interpolation');
  }
});

Config usage (same plugins list for extract + lint):

import { defineConfig } from 'i18next-cli';
import { vueLintPlugin } from './plugins/vue-lint-plugin.mjs';

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

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()
  ]
});

Location Metadata Tracking

Track where each translation key is used in your codebase with a custom metadata plugin.

Example Plugin Implementation:

import { readFile, writeFile, mkdir } from 'node:fs/promises';
import { dirname } from 'node:path';
import type { Plugin } from 'i18next-cli';

interface LocationMetadataOptions {
  /** Output path for the metadata file (default: 'locales/metadata.json') */
  output?: string;
  /** Include line and column numbers (default: true) */
  includePosition?: boolean;
}

export const locationMetadataPlugin = (options: LocationMetadataOptions = {}): Plugin => {
  const {
    output = 'locales/metadata.json',
    includePosition = true,
  } = options;

  return {
    name: 'location-metadata',

    async onEnd(keys) {
      const metadata: Record<string, any> = {};

      for (const [uniqueKey, extractedKey] of keys.entries()) {
        const { key, ns, locations } = extractedKey;

        // Skip keys without location data
        if (!locations || locations.length === 0) {
          continue;
        }

        // Format location data
        const locationData = locations.map(loc => {
          if (includePosition && loc.line !== undefined) {
            return `${loc.file}:${loc.line}:${loc.column ?? 0}`;
          }
          return loc.file;
        });

        // Organize metadata
        const namespace = ns || 'translation';
        if (!metadata[namespace]) {
          metadata[namespace] = {};
        }
        metadata[namespace][key] = locationData;
      }

      // Write metadata file
      await mkdir(dirname(output), { recursive: true });
      await writeFile(output, JSON.stringify(metadata, null, 2), 'utf-8');
      
      console.log(`📍 Location metadata written to ${output}`);
    }
  };
};

Configuration:

// i18next.config.ts
import { defineConfig } from 'i18next-cli';
import { locationMetadataPlugin } from './plugins/location-metadata.mjs';

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

Example Output (locales/metadata.json):

{
  "translation": {
    "app.title": [
      "src/App.tsx:12:15",
      "src/components/Header.tsx:8:22"
    ],
    "user.greeting": [
      "src/pages/Profile.tsx:45:10"
    ]
  },
  "common": {
    "button.save": [
      "src/components/SaveButton.tsx:18:7",
      "src/forms/UserForm.tsx:92:5"
    ]
  }
}

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;

YAML Translation Files

For projects that prefer YAML for better readability and compatibility with other tools, you can configure the CLI to output YAML files instead of JSON.

Configuration (i18next.config.ts):

export default defineConfig({
  extract: {
    output: 'locales/{{language}}/{{namespace}}.yaml', // Use .yaml or .yml
    outputFormat: 'yaml', // Optional - inferred from file extension
  }
});

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

app:
  title: My Application
  description: Welcome to our app
button:
  save: Save
  cancel: Cancel

💡 Note: Both .yaml and .yml extensions are supported and preserved. The outputFormat: 'yaml' option is optional when using these extensions - the format is automatically inferred from the file extension.

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 { anyFileUpdated, hasErrors } = await runExtractor(config);
console.log('Files updated:', anyFileUpdated);

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

// Run linting and get results
const { success, message, files } = await runLinter(config);
if (!success) {
  console.error(message);
  for (const [filename, issues] of Object.entries(files)) {
    console.error(`${issues.length} issues found in ${filename}.`);
  }
}

// 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 and return results
• runSyncer(config) - Sync translation files
• runStatus(config, options?) - Get translation status
• runTypesGenerator(config) - Generate types

Advanced Usage

Linter - Class that lints your codebase and emits events along the way

Example usage

import { Linter } 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',
  },
};

const linter = new Linter(config);

linter.addEventListener('progress', ({ message }) => console.log(message));

await linter.run();

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.

Known plugins

• i18next-cli-plugin-svelte — a simple plugin to extract translation keys from Svelte components
• rsbuild-plugin-i18next-extractor — A Rsbuild plugin that leverages the Rspack module graph to extract only the i18n translations that are actually imported and used in your code, preventing unused translations from being bundled.
• i18next-cli-vue — i18next-cli plugin for extracting i18n keys from Vue SFC files, applicable to vue2 and vue3

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