# Internationalization

Strapi provides built-in support for detecting user language preferences and translating
static words/sentences.

## i18n settings

Settings for localization/internationalization may be configured in `strapi.config.i18n`.
The most common reason you'll need to modify these settings is to edit the list of your
application's supported locales and/or the location of your translation stringfiles.

## Locales

Strapi reads JSON-formatted translation files from your project's `./config/locales`
directory. Each file corresponds with a locale (usually a language) that your backend will support.
These files contain locale-specific strings (as JSON key-value pairs) that you can use in your
views, controllers, etc.

When your server is in `production` mode it will read these files only once and then cache
the result. It will not write any updated strings when in `production` mode.

Otherwise, the files will be read on every instantiation of the `i18n` object.
Additionally newly-detected strings will be automatically added, and written out,
to the locale JSON files.

These files contain locale-specific strings (as JSON key-value pairs) that you can use in your views,
controllers, etc. Here is an example locale file (`./config/locales/fr.json`):

```js
{
  "Hello!": "Bonjour!",
  "Hello %s, how are you today?": "Bonjour %s, comment allez-vous aujourd'hui ?"
}
```

Note that the keys in your stringfiles are case sensitive and require exact matches.
There are a few different schools of thought on the best approach here, and it really depends on
who/how often you'll be editing the stringfiles in the future. Especially if you'll be
editing the translations by hand, simpler, all-lowercase key names may be preferable for maintainability.

For example, here's another pass at `./config/locales/fr.json`:

```js
{
  "hello": "Bonjour!",
  "hello-how-are-you-today": "Bonjour %s, comment allez-vous aujourd'hui ?"
}
```

And here's `./config/locales/en.json`:

```js
{
  "hello": "Hello!",
  "hello-how-are-you-today": "Hello %s, how are you today?"
}
```

You can also nest locale strings. But a better approach would be to use `.` to represent nested strings.
For example, here's the list of labels for the index page of a user controller:

```js
{
  "user.index.label.id": "User ID",
  "user.index.label.name": "User Name"
}
```

## Translate responses

Locales are accessible from everywhere in your application.

```js
this.body = this.i18n.__('hello-how-are-you-today', 'John');
// => "Hello John, how are you today?"
```

Different plural forms are supported as a response to `count` with `this.i18n.__n(one, other, count)`.

Use `this.i18n.__n()` as you would use `this.i18.__()` directly:

```js
this.body = this.i18n.__n('%s cat', '%s cats', 1);
// => "1 cat"

this.body = this.i18n.__n('%s cat', '%s cats', 3);
// => "3 cats"
```

Or from locales:

```js
{
  "catEat": {
    "one": "%d cat eats the %s",
    "other": '%d cats eat the %s'
  }
}
```

```js
this.body = this.i18n.__n('catEat', 10, 'mouse');
// => "10 cats eat the mouse"
```