Android runs on many devices in many regions. To reach the most users, make sure that your app handles text, audio files, numbers, currency, and graphics in ways appropriate to the locales where your app is used.
This page describes best practices for localizing Android apps.
You need to have a working knowledge of either Kotlin or the Java programming language and be familiar with Android resource loading, declaring user interface elements in XML, development considerations such as the activity lifecycle, and general principles of internationalization and localization.
It is good practice to use the Android resource framework to separate the localized aspects of your app as much as possible from core app functionality.
- Put most or all of the contents of your app's user interface into resource files, as described on this page and in the App resources overview.
- The behavior of the user interface, on the other hand, is driven by your Kotlin-based or Java-based code. For example, if users input data that needs to be formatted or sorted differently depending on locale, then you use Kotlin or the Java programming language to handle the data programmatically. This page doesn't cover how to localize your Kotlin-based or Java-based code.
For a short guide to localizing strings in your app, see Support different languages and cultures.
Overview: Resource switching in Android
Resources are text strings, layouts, sounds, graphics, and any other static data that your Android app needs. An app can include multiple sets of resources, each customized for a different device configuration. When a user runs the app, Android automatically selects and loads the resources that best match the device.
This page focuses on localization and locale. For a complete description of resource-switching and all the types of configurations that you can specify, such as screen orientation or touchscreen type, see Provide alternative resources.
When you write your app, you create default and alternative resources
for your app to use. When users run your app, the Android system
selects which resources to load based on the device's locale.
To create resources, you place files within
specially named subdirectories of the project's
Why default resources are important
When the app runs in any locale that you haven't provided
locale-specific text for, Android loads the default strings from
res/values/strings.xml. If this default file is absent, or if it's
missing a string that your app needs, then your app doesn't run
and shows an error. The following example illustrates what can happen when the
default text file is incomplete.
An app's Kotlin-based or Java-based code refers to just two strings,
text_b. The app includes a localized resource file
res/values-en/strings.xml) that defines
text_b in English. The app also includes a default
resource file (
res/values/strings.xml) that includes a
text_a, but not for
- When this app is launched on a device with locale set to English,
the app might run without a problem, because
res/values-en/strings.xmlcontains both of the needed text strings.
- However, when this app is launched on a device set to a language other than English, the user sees an error message and a Force Close button. The app doesn't load.
To prevent this situation, make sure that a
file exists and that it defines every needed string. This situation applies to
all types of resources, not just strings: you need to create a set of default
resource files containing all the resources that your app calls on,
such as layouts, drawables, or animations. For information about testing, see the
Test for default resources section.
Use resources for localization
This section discusses how to create default resources as well as alternative resources. It also explains how resources are assigned precedence and how you refer to your resources in code.
Create default resources
Put the app's default text in
res/values/strings.xml. For these strings, use the
default language—the language you expect most of your
app's users to speak.
The default resource set also includes any default drawables and layouts and can include other types of resources such as animations. These resources go in the following directories:
res/drawable/: required directory holding at least one graphic file, for the app's icon on Google Play
res/layout/: required directory holding an XML file that defines the default layout
res/anim/: required if you have any
res/xml/: required if you have any
res/raw/: required if you have any
Tip: In your code, examine each reference to an Android resource. Make sure that a default resource is defined for each one. Also make sure that the default string file is complete: a localized string file can contain a subset of the strings, but the default string file must contain them all.
Create alternative resources
A large part of localizing an app is providing alternative text for different languages. In some cases, you also provide alternative graphics, sounds, layouts, and other locale-specific resources.
An app can specify many
directories, each with different qualifiers. To create an alternative resource for
a different locale, you use a qualifier that specifies a language or a
language-region combination. The name of a resource directory must conform
to the naming scheme described in
alternative resources, or else your app can't compile.
Suppose that your app's default language is English and that
you want to localize all the text in your app to French and all
the text except the app's title to
Japanese. In this case, you create three
files, each stored in a locale-specific resource directory:
Contains English text for all the strings that the app uses, including text for a string named
Contain French text for all the strings, including
Contain Japanese text for all the strings except
If your Kotlin-based or Java-based code refers to
R.string.title, here is what
happens at runtime:
- If the device is set to any language other than French, Android loads
- If the device is set to French, Android loads
If the device is set to Japanese, Android looks for
title in the
res/values-ja/strings.xml file. But
because no such string is included in that file, Android falls back to the
default, and loads the
title in English from the
Which resources take precedence?
If multiple resource files match a device's configuration, Android follows a set of rules in deciding which file to use. Among the qualifiers that can be specified in a resource directory name, locale almost always takes precedence.
Assume that an app includes a default set of graphics and two other sets of graphics, each optimized for a different device setup:
Contains default graphics.
Contains graphics optimized for use with a device that expects input from a stylus and has a QVGA low-density screen in landscape orientation.
Contains graphics optimized for use with Japanese.
If the app runs on a device that is configured to use Japanese,
Android loads graphics from
res/drawable-ja/, even if the device
happens to be one that expects input from a stylus and has a QVGA low-density
screen in landscape orientation.
Exception: The only qualifiers that take precedence over locale in the selection process are mobile country code (MCC) and mobile network code (MNC).
Assume that you have the following situation:
- The app code calls for
- Two relevant resource files are available:
res/values-mcc404/strings.xml, which includes
text_ain the app's default language, in this case English.
res/values-hi/strings.xml, which includes
- The app is running on a device that has the following
- The SIM card is connected to a mobile network in India (MCC 404).
- The language is set to Hindi (
res/values-mcc404/strings.xml (in English), even if the device is
configured for Hindi. That is because in the resource-selection process, Android
prefers an MCC match over a language match.
The selection process isn't always as straightforward as these examples suggest. For a more nuanced description of the process, see How android finds the best-matching resource. All the qualifiers are described and listed in order of precedence in the App resources overview.
Refer to resources in code
In your app's Kotlin-based or Java-based code, you refer to resources using the syntax
For more information, see
Access your app resources.
Manage strings for localization
This section describes best practices for managing your strings related to localization.
Move all strings into strings.xml
As you build your apps, don't hardcode any strings. Instead, declare all your
strings as resources in a default
strings.xml file, which makes it easy to update
and localize them. Strings in the
strings.xml file can be easily extracted,
translated, and integrated back into your app, with appropriate qualifiers, without any
changes to the compiled code.
If you generate images with text, put those strings in
strings.xml as well, and
regenerate the images after translation.
Follow Android guidelines for UI strings
As you design and develop your UIs, pay close attention to how you talk to your user. In general, use a succinct style that is friendly but brief, and use a consistent style throughout your UIs.
Make sure that you read and follow the Material Design recommendations for writing style and word choice. Doing so makes your apps appear more polished to the user and helps users understand your UI more quickly.
Also, always use Android standard terminology wherever possible, such as for UI elements like the app bar, options menu, system bar, and notifications. Using Android terms correctly and consistently makes translation easier and results in a better end-product for users.
Provide sufficient context for declared strings
As you declare strings in your
strings.xml file, make sure to describe the context
in which the string is used. This information is invaluable to the translator and results in
better quality translation. It also helps you manage your strings more effectively.
Here is an example:
<!-- The action for submitting a form. This text is on a button that can fit 30 chars --> <string name="login_submit_button">Sign in</string>
Consider providing context information like the following:
- What is this string for? When and where is it presented to the user?
- Where is this in the layout? For example, translations are less flexible in buttons than in text boxes.
Mark message parts that aren't to be translated
Often, strings contain text that isn't meant to be translated into other languages. Common examples are a piece of code, a placeholder for a value, a special symbol, or a name. As you prepare your strings for translation, look for and mark text that must remain as-is, without translation, so that the translator doesn't change it.
To mark text that isn't to be translated, use an
placeholder tag. Here is an example tag that indicates that the text
to be changed during translation, to avoid breaking the message:
<string name="countdown"> <xliff:g id="time" example="5 days">%1$s</xliff:g> until holiday </string>
When you declare a placeholder tag, add an ID attribute that explains what the placeholder is for. If your app later replaces the placeholder value, be sure to provide an example attribute to clarify the expected use.
Here are some more examples of placeholder tags:
<resources xmlns:xliff="urn:oasis:names:tc:xliff:document:1.2"> <!-- Example placeholder for a special Unicode symbol --> <string name="star_rating">Check out our 5 <xliff:g id="star">\u2605</xliff:g> </string> <!-- Example placeholder for a URL --> <string name="app_homeurl"> Visit us at <xliff:g id="application_homepage">http://my/app/home.html</xliff:g> </string> <!-- Example placeholder for a name --> <string name="prod_name"> Learn more at <xliff:g id="prod_gamegroup">Game Group</xliff:g> </string> <!-- Example placeholder for a literal --> <string name="promo_message"> Please use the "<xliff:g id="promotion_code">ABCDEFG</xliff:g>" to get a discount. </string> ... </resources>
For a complete overview of the process of localizing and distributing an Android app, see Translate and localize your app.
Follow these tips as you localize your app.
Design your app to work in any locale
Don't assume anything about the device on which a user runs your app. The device might have hardware that you were not anticipating, or it might be set to a locale that you didn't plan for or that you can't test. Design your app so that it functions normally or fails gracefully no matter what device it runs on.
Important: Make sure that your app
includes a full set of default resources: include
res/drawable/ and a
res/values/ folders without any
additional modifiers in the folder names, that contain all the images and text
that your app needs.
If an app is missing even one default resource, it doesn't run on a
device that is set to an unsupported locale. For example, if the
res/values/strings.xml default file lacks one string that
the app needs, when the app runs in an unsupported locale and
attempts to load
res/values/strings.xml, the user sees an error
message and a Force Close button.
For more information, see the Test for default resources section.
Design a flexible layout
If you need to rearrange your layout to fit a certain language,
you can create an alternative layout for that language, such as
res/layout-de/main.xml for a German-language layout. However, doing this
can make your app harder to maintain. It is better to create a single
layout that is more flexible.
Another typical situation is a language that requires something different in its layout. For example, you might have a contact form that includes two name fields when the app runs in Japanese, but three name fields when the app runs in some other language. You can handle this in either of two ways:
- Create one layout with a field that you can programmatically enable or disable, based on the language.
- Have the main layout include another layout that includes the changeable field. The second layout can have different configurations for different languages.
Avoid creating more resource files and text strings than you need
You probably don't need to create a locale-specific alternative for every
resource in your app. For example, the layout defined in the
res/layout/main.xml file might work in any locale, in which case
there is no need to create any alternative layout files.
Also, you might not need to create alternative text for every string. For example, assume the following:
- Your app's default language is American English. Every string that
the app uses is defined, using American English spellings, in
- For a few important phrases, you want to provide British English spelling. You want these alternative strings to be used when your app runs on a device in the United Kingdom.
To do this, create a small file called
res/values-en-rGB/strings.xml that includes only the strings that
are different when the app runs in the U.K. For all the rest of
the strings, the app falls back to the defaults and uses what is
Use the Android Context object for manual locale lookup
You can look up the locale using the
that Android makes available, as shown in the following example:
val primaryLocale: Locale = context.resources.configuration.locales val locale: String = primaryLocale.displayName
Locale primaryLocale = context.getResources().getConfiguration().getLocales().get(0); String locale = primaryLocale.getDisplayName();
Use the app translation service
The App Translation Service is integrated into the Play Console. It lets you get an instant quote and place an order with a translation company. You can order translations into one or more languages for app UI strings, Play Store Listing text, IAP names, and ad campaign text.
Test localized apps
Test your localized app on a device or using the Android Emulator. In particular, test your app to ensure that all the necessary default resources are included.
Test on a device
Bear in mind that the device you are testing on might be significantly different from the devices available to consumers in other places. The locales available on your device can differ from those available on other devices. Also, the resolution and density of the device screen might differ, which can affect the display of strings and drawables in your UI.
To change the locale or language on a device, use the Settings app.
Test on an emulator
For details about using the emulator, see Run apps on the Android Emulator.
Create and using a custom locale
A "custom" locale is a language or region combination that the Android system image doesn't explicitly support. You can test how your app runs in a custom locale by creating a custom locale in the emulator. There are two ways to do this:
- Use the Custom Locale app, which is accessible from the app tab. After you create a custom locale, switch to it by touching & holding the locale name.
- Change to a custom locale from the
adbshell, as described in the following section.
When you set the emulator to a locale that isn't available in the Android system image, the system itself displays in its default language. Your app, however, localizes properly.
Change the emulator locale from the adb shell
To change the locale in the emulator by using the
adb shell, do the following:
- Pick the locale you want to test and determine its BCP-47 language tag,
fr-CAfor Canadian French.
- Launch an emulator.
- From a command-line shell on the host computer, run the following
or, if you have a device attached, specify that you want the emulator by adding the
adb -e shell
- At the
adbshell prompt (
#), run this command:
setprop persist.sys.locale [BCP-47 language tag];stop;sleep 5;startReplace the bracketed sections with the appropriate codes from Step 1.
For instance, to test in Canadian French:
setprop persist.sys.locale fr-CA;stop;sleep 5;start
This causes the emulator to restart. Once the Home screen appears again, re-launch your app, and the app launches with the new locale.
Test for default resources
To test whether an app includes every string resource that it needs, do the following:
- Set the emulator or device to a language that your app doesn't
support. For example, if the app has French strings in
res/values-fr/but doesn't have any Spanish strings in
res/values-es/, then set the emulator's locale to Spanish. You can use the Custom Locale app to set the emulator to an unsupported locale.
- Run the app.
- If the app shows an error message and a Force Close button, it might
be looking for a string that isn't available. Make sure that your
res/values/strings.xmlfile includes a definition for every string that the app uses.
If the test is successful, repeat it for other types of configurations. For
example, if the app has a layout file called
res/layout-land/main.xml but doesn't contain a file called
res/layout-port/main.xml, then set the emulator or device to
portrait orientation and see whether the app runs.