# Startup Locale Selectors

The Locale Selector is part of the [Localization Settings](LocalizationSettings.md). It determines which [Locale](Locale.md) Unity should use when the application first starts or an active Locale isn't selected. For example, you might want to use a default Locale, or attempt to use the Locale that the player is using on their device.

> [!NOTE]
> The Localization Settings query each selector in the list, starting at the top (index 0). If a selector doesn't return a locale (null), then it queries the next, until it finds a valid Locale or it reaches the end of the list. This lets you create fallback behaviors when Unity is selecting which Locale to use.

![Configure the Locale Selectors in the Localization Project Settings window.](images/LocalizationSettings_LocaleSelector.png)

By default, you can choose from the following Locale Selectors.

* [Command Line Locale Selector](#command-line-locale-selector)
* [System Locale Selector](#system-locale-selector)
* [Specific Locale Selector](#specific-locale-selector)
* [Player Pref Locale Selector](#player-pref-locale-selector)

You can create additional custom selectors using the [IStartupLocaleSelector](xref:UnityEngine.Localization.Settings.IStartupLocaleSelector) interface.

## Command Line Locale Selector

The Command Line Locale Selector lets you set the Locale through a command line argument when launching the application. The locale provided through command line should match the Locale Code.
For example `-language=en-GB` would match English(United Kingdom), `-language=ja` would match Japanese.
The default argument is `-language=`. You can configure this in the **Command Line Argument** field.

## System Locale Selector

The System Locale Selector attempts to detect the locale of the device and find a match.
The System Locale Selector queries different APIs until it finds a matching locale or a suitable fallback locale.

![The System Locale Selector queries different APIs until it finds a locale or a suitable fallback locale.](images/SystemLocaleSelectorOverview.dot.svg)

- **iOS - Preferred Language**: Unity queries the [iOS Preferred Language](https://developer.apple.com/news/?id=u2cfuj88).
- **Android - Device Language**: Unity queries the [Android getDefault](https://developer.android.com/reference/java/util/Locale#getDefault(java.util.Locale.Category)) value.
- **System Culture**: Unity uses the [CultureInfo.CurrentUICulture](https://docs.microsoft.com/en-us/dotnet/api/system.globalization.cultureinfo.currentuiculture) value.
- **System Language**: Unity uses the [SystemLanguage](https://docs.unity3d.com/ScriptReference/SystemLanguage.html) value as its final check.

## Specific Locale Selector

The Specific Locale Selector selects a specified locale. You can use this to ensure that a Locale is always selected when all other selectors have failed. The selected locale can be configured through the **Locale Id** field.

## Player Pref Locale Selector

The Player Pref Locale Selector uses Unity's [PlayerPrefs](https://docs.unity3d.com/ScriptReference/PlayerPrefs.html) to store and retrieve the selected locale between game sessions, enabling the game to remember the language preference of the player across different sessions. The selected locale code is stored as a string using [PlayerPrefs.SetString](https://docs.unity3d.com/ScriptReference/PlayerPrefs.SetString.html), which allows Unity to guarantee that the next time the player launches the game, it will use the same language they previously chose.