---
createdAt: 2026-01-21
updatedAt: 2026-01-21
title: fastify-intlayer Package Documentation
description: Fastify plugin for Intlayer, providing translation functions and locale detection.
keywords:
  - fastify-intlayer
  - fastify
  - plugin
  - internationalization
  - i18n
slugs:
  - doc
  - packages
  - fastify-intlayer
  - exports
history:
  - version: 8.0.0
    date: 2026-01-21
    changes: "Unified documentation for all exports"
---

# fastify-intlayer Package

The `fastify-intlayer` package provides a plugin for Fastify applications to handle internationalisation. It detects the user's locale and decorates the request object.

## Installation

```bash
npm install fastify-intlayer
```

## Exports

### Plugin

Import:

```tsx
import "fastify-intlayer";
```

| Function   | Description                                                                                                                                                                                                                                                                                                            | Related documentation                                                                                              |
| ---------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------ |
| `intlayer` | Fastify plugin that integrates Intlayer into your Fastify application. Handles locale detection from storage (cookies, headers), decorates the request object with `intlayer` data containing `t`, `getIntlayer`, and `getDictionary`, and sets up CLS namespace for programmatic access during the request lifecycle. | [intlayer](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en-GB/packages/fastify-intlayer/intlayer.md) |

### Functions

Import:

```tsx
import "fastify-intlayer";
```

| Function        | Description                                                                                                                                                                                                                                       | Related Doc                                                                                               |
| --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------- |
| `t`             | Global translation function that retrieves content for the current locale in Fastify. Utilises CLS (Async Local Storage) and must be used within a request context managed by the `intlayer` plugin. Can also be accessed via `req.intlayer.t`.   | [translation](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en-GB/dictionary/translation.md) |
| `getIntlayer`   | Retrieves a dictionary by its key from the generated declaration and returns its content for the specified locale. Optimised version of `getDictionary`. Uses CLS to access request context. Can also be accessed via `req.intlayer.getIntlayer`. | -                                                                                                         |
| `getDictionary` | Processes dictionary objects and returns content for the specified locale. Processes `t()` translations, enumerations, Markdown, HTML, etc. Uses CLS to access the request context. It can also be accessed via `req.intlayer.getDictionary`.     | -                                                                                                         |
