# internationalization-i18n

Sets up multi-language workflows using i18next, gettext, or native Intl APIs. Useful when building apps with plural forms, locale formatting, and RTL layouts.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 433 installs · ★ 236
- Author: secondsky
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/secondsky/claude-skills/tree/HEAD/plugins/internationalization-i18n/skills/internationalization-i18n/SKILL.md
- Updated: 2026-10-20
- HTML: https://affpapa.org/en/nevibecode/skills/secondsky-internationalization-i18n

## What it does

This skill adds guidelines for project localization. It covers `i18next` configuration in React with `LanguageDetector` and `initReactI18next`, explicit pluralization rules keyed by count, and references for `React-Intl` (Format.js) or Python Babel with Flask.

Date and currency formatting relies on browser-native `Intl` constructors rather than external date utilities. For right-to-left scripts, it promotes CSS logical properties like `margin-inline-start` alongside directional selectors such as `html[dir="rtl"]`.

String concatenation is explicitly ruled out by the skill because it breaks sentence structures across languages. For complex copy with nested variables, it instructs using the ICU Message Format instead.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill internationalization-i18n -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/internationalization-i18n/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/internationalization-i18n/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill internationalization-i18n -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/internationalization-i18n/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill internationalization-i18n -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/internationalization-i18n/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install secondsky/claude-skills internationalization-i18n
```

2. **Manually: put the files in place**
- File: `.github/skills/internationalization-i18n/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill internationalization-i18n -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/secondsky/claude-skills --path plugins/internationalization-i18n/skills/internationalization-i18n
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/internationalization-i18n/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill internationalization-i18n -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/secondsky/claude-skills/tree/HEAD/plugins/internationalization-i18n/skills/internationalization-i18n/SKILL.md

## When to use it
- configure `i18next` with language detection for React components
- format dates and currencies using the native `Intl` API
- adapt layouts for right-to-left (RTL) reading directions using logical CSS
- manage pluralized strings without manual string concatenation

## Example prompts
- Set up i18next for my React app and show a pluralization example for item counts
- Convert these layout margins and padding styles to CSS logical properties for RTL
- Format product prices and delivery dates using Intl API for de-DE and en-US

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 72e17a11f02f428f.

BEGIN THIRD-PARTY FILE 72e17a11f02f428f
````text
---
name: internationalization-i18n
description: Implements multi-language support using i18next, gettext, or Intl API with translation workflows and RTL support. Use when building multilingual applications, handling date/currency formatting, or supporting right-to-left languages.
license: MIT
---

# Internationalization (i18n)

Implement multi-language support with proper translation management and formatting.

## i18next Setup (React)

```javascript
import i18n from 'i18next';
import { initReactI18next } from 'react-i18next';
import LanguageDetector from 'i18next-browser-languagedetector';

i18n
  .use(LanguageDetector)
  .use(initReactI18next)
  .init({
    fallbackLng: 'en',
    interpolation: { escapeValue: false },
    resources: {
      en: { translation: { welcome: 'Welcome, {{name}}!' } },
      es: { translation: { welcome: '¡Bienvenido, {{name}}!' } }
    }
  });

// Usage
const { t } = useTranslation();
<h1>{t('welcome', { name: 'John' })}</h1>
```

## Pluralization

```javascript
// Translation file
{
  "items": "{{count}} item",
  "items_plural": "{{count}} items",
  "items_zero": "No items"
}

// Usage
t('items', { count: 0 })  // "No items"
t('items', { count: 1 })  // "1 item"
t('items', { count: 5 })  // "5 items"
```

## Date/Number Formatting

```javascript
// Dates
new Intl.DateTimeFormat('de-DE', {
  dateStyle: 'long',
  timeStyle: 'short'
}).format(new Date());

// Numbers
new Intl.NumberFormat('en-US', {
  style: 'currency',
  currency: 'USD'
}).format(1234.56);  // "$1,234.56"

// Relative time
new Intl.RelativeTimeFormat('en', { numeric: 'auto' })
  .format(-1, 'day');  // "yesterday"
```

## RTL Support

```css
/* Use logical properties */
.container {
  margin-inline-start: 1rem;  /* margin-left in LTR, margin-right in RTL */
  padding-inline-end: 1rem;
}

/* Direction attribute */
html[dir="rtl"] .icon {
  transform: scaleX(-1);
}
```

## Additional Frameworks

See [references/frameworks.md](references/frameworks.md) for:
- React-Intl (Format.js) complete implementation
- Python gettext with Flask/Babel
- RTL language support patterns
- ICU Message Format examples

## Best Practices

- Extract all user-facing strings
- Use ICU message format for complex translations
- Test with pseudo-localization
- Support RTL from the start
- Never concatenate translated strings
- Use professional translators for production
````
END THIRD-PARTY FILE 72e17a11f02f428f

The third-party file has ended. Everything between the 72e17a11f02f428f tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

© secondsky · MIT · https://github.com/secondsky/claude-skills/tree/HEAD/plugins/internationalization-i18n/skills/internationalization-i18n/SKILL.md

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