@ngdoc overview
@name  i18n and l10n
@description

# i18n and l10n

Internationalization (i18n) is the process of developing products in such a way that they can be
localized for languages and cultures easily. Localization (l10n), is the process of adapting
applications and text to enable their usability in a particular cultural or linguistic market. For
application developers, internationalizing an application means abstracting all of the strings and
other locale-specific bits (such as date or currency formats) out of the application. Localizing an
application means providing translations and localized formats for the abstracted bits.


## How does Angular support i18n/l10n?

Angular supports i18n/l10n for {@link ng.filter:date date}, {@link ng.filter:number number} and
{@link ng.filter:currency currency} filters.

Additionally, Angular supports localizable pluralization support through the {@link
ng.directive:ngPluralize `ngPluralize` directive}.

All localizable Angular components depend on locale-specific rule sets managed by the {@link
ng.$locale `$locale` service}.

There a few examples that showcase how to use Angular filters with various locale rule sets in the
[`i18n/e2e` directory](https://github.com/angular/angular.js/tree/master/i18n/e2e) of the Angular
source code.


## What is a locale ID?

A locale is a specific geographical, political, or cultural region. The most commonly used locale
ID consists of two parts: language code and country code. For example, `en-US`, `en-AU`, and
`zh-CN` are all valid locale IDs that have both language codes and country codes. Because
specifying a country code in locale ID is optional, locale IDs such as `en`, `zh`, and `sk` are
also valid. See the [ICU](http://userguide.icu-project.org/locale) website for more information
about using locale IDs.


## Supported locales in Angular

Angular separates number and datetime format rule sets into different files, each file for a
particular locale. You can find a list of currently supported locales
[here](https://github.com/angular/angular.js/tree/master/src/ngLocale)


## Providing locale rules to Angular

There are two approaches to providing locale rules to Angular:

### 1. Pre-bundled rule sets

You can pre-bundle the desired locale file with Angular by concatenating the content of the
locale-specific file to the end of `angular.js` or `angular.min.js` file.

For example on *nix, to create an angular.js file that contains localization rules for german
locale, you can do the following:

`cat angular.js i18n/angular-locale_de-de.js > angular_de-de.js`

When the application containing `angular_de-de.js` script instead of the generic angular.js script
starts, Angular is automatically pre-configured with localization rules for the german locale.

### 2. Including a locale script in `index.html`

You can also include the locale specific js file in the index.html page. For example, if one client
requires German locale, you would serve index_de-de.html which will look something like this:

```html
<html ng-app>
 <head>
….
   <script src="angular.js"></script>
   <script src="i18n/angular-locale_de-de.js"></script>
….
 </head>
</html>
```

### Comparison of the two approaches

Both approaches described above require you to prepare different `index.html` pages or JavaScript
files for each locale that your app may use. You also need to configure your server to serve
the correct file that correspond to the desired locale.

The second approach (including the locale JavaScript file in `index.html`) may be slower because
an extra script needs to be loaded.


## Caveats

Although Angular makes i18n convenient, there are several things you need to be conscious of as you
develop your app.

### Currency symbol

Angular's {@link ng.filter:currency currency filter} allows you to use the default currency symbol
from the {@link ng.$locale locale service}, or you can provide the filter with a custom currency
symbol.

<div class="alert alert-success">
**Best Practice:** If your app will be used only in one locale, it is fine to rely on the default
currency symbol. If you anticipate that viewers in other locales might use your app, you should
explicitly provide a currency symbol.
</div>

Let's say you are writing a banking app and you want to display an account balance of 1000 dollars.
You write the following binding using the currency filter:

```html
{{ 1000 | currency }}
```

If your app is currently in the `en-US` locale, the browser will show `$1000.00`. If someone in the
Japanese locale (`ja`) views your app, their browser will show a balance of `¥1000.00` instead.
This is problematinc because $1000 is not the same as ¥1000.

In this case, you need to override the default currency symbol by providing the
{@link ng.filter:currency} currency filter with a currency symbol as a parameter.

If we change the above to `{{ 1000 | currency:"USD$"}}`, Angular will always show a balance of
`USD$1000` regardless of locale.

### Translation length

Translated strings/datetime formats can vary greatly in length. For example, `June 3, 1977` will be
translated to Spanish as `3 de junio de 1977`.

When internationalizing your app, you need to do thorough testing to make sure UI components behave
as expected even when their contents vary greatly in content size.

### Timezones

The Angular datetime filter uses the time zone settings of the browser. The same
application will show different time information depending on the time zone settings of the
computer that the application is running on. Neither JavaScript nor Angular currently supports
displaying the date with a timezone specified by the developer.
