Tools attributes reference

While Jetpack Compose handles UI design-time tooling directly in Kotlin, the tools: namespace is still essential for project-level configurations. Standard Android XML files, like AndroidManifest.xml and res/raw/keep.xml, use tools: attributes to manage Lint warnings and configure the resource shrinker.

When you build your app, the build tools remove these attributes so that there is no effect on your APK size or runtime behavior.

To use these attributes, add the tools namespace to the root element of each XML file where you'd like to use them, as shown here:

<RootTag xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" >

Error-handling attributes

The following attributes help suppress lint warning messages:

tools:ignore

Intended for: Any element

Used by: Lint

This attribute accepts a comma-separated list of lint issue IDs that you'd like the tools to ignore on this element or any of its descendants.

For example, you can tell the tools to ignore the MissingTranslation error:

<string name="show_all_apps" tools:ignore="MissingTranslation">All</string>

tools:targetApi

Intended for: Any element

Used by: Lint

This attribute works the same as the @TargetApi annotation in Java code or the @RequiresApi annotation in Kotlin code. It lets you specify the API level (either as an integer or as a code name) that supports this element.

This tells the lint tools that you believe this element and any children are used only on the specified API level or higher. This stops lint from warning you if that element or its attributes are not available on the API level you specify as your minSdkVersion.

For example, you might use this attribute because you are declaring a <service> in your AndroidManifest.xml that uses a foreground service type only available on API level 34 and higher, but your project's minSdkVersion is lower:

<service
    android:name=".playback.MediaPlaybackService"
    android:foregroundServiceType="mediaPlayback"
    xmlns:tools="http://schemas.android.com/tools"
    tools:targetApi="34" />

tools:locale

Intended for: <resources>

Used by: Lint, Android Studio editor

This tells the tools what the default language or locale is for the resources in the given <resources> element to avoid warnings from the spellchecker. The tool otherwise assumes the language is English.

The value must be a valid locale qualifier.

For example, you can add this to your default values/strings.xml file to indicate that the language used for the default strings is Spanish rather than English:

<resources xmlns:tools="http://schemas.android.com/tools"
    tools:locale="es">

Resource shrinking attributes

The following attributes let you enable strict reference checks and declare whether to keep or discard certain resources when using resource shrinking.

To enable resource shrinking, set the shrinkResources property to true in your build.gradle file, alongside minifyEnabled for code shrinking.

For example:

android {
    ...
    buildTypes {
        release {
            shrinkResources true
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'),
                    'proguard-rules.pro'
        }
    }
}

android {
    ...
    buildTypes {
        getByName("release") {
            isShrinkResources = true
            isMinifyEnabled = true
            proguardFiles(
                getDefaultProguardFile("proguard-android.txt"),
                "proguard-rules.pro"
            )
        }
    }
}

tools:shrinkMode

Intended for: <resources>

Used by: Build tools with resource shrinking

This attribute lets you specify whether the build tools should use the following:

• Safe mode: Keep all resources that are explicitly cited and that might be referenced dynamically with a call to Resources.getIdentifier().
• Strict mode: Keep only the resources that are explicitly cited in code or in other resources.

The default is to use safe mode (shrinkMode="safe"). To instead use strict mode, add shrinkMode="strict" to the <resources> tag as shown here:

<?xml version="1.0" encoding="utf-8"?>
<resources xmlns:tools="http://schemas.android.com/tools"
    tools:shrinkMode="strict" />

When you enable strict mode, you might need to use tools:keep to keep resources that were removed but that you actually want, and use tools:discard to explicitly remove even more resources.

For more information, see Shrink your resources.

tools:keep

Intended for: <resources>

Used by: Build tools with resource shrinking

When using resource shrinking to remove unused resources, this attribute lets you specify resources to keep, typically because they are referenced in an indirect way at runtime, such as by passing a dynamically generated resource name to Resources.getIdentifier().

To use, create an XML file in your resources directory (for example, res/raw/keep.xml) with a <resources> tag and specify each resource to keep in the tools:keep attribute as a comma-separated list. You can use the asterisk character as a wildcard.

For example:

<?xml version="1.0" encoding="utf-8"?>
<resources xmlns:tools="http://schemas.android.com/tools"
    tools:keep="@layout/used_1,@layout/used_2,@layout/*_3" />

For more information, see Shrink your resources.

tools:discard

Intended for: <resources>

Used by: Build tools with resource shrinking

When using resource shrinking to remove unused resources, this attribute lets you specify resources you want to manually discard, typically because the resource is referenced but in a way that does not affect your app or because the Gradle plugin has incorrectly deduced that the resource is referenced.

To use, create an XML file in your resources directory (for example, res/raw/keep.xml) with a <resources> tag and specify each resource to discard in the tools:discard attribute as a comma-separated list. You can use the asterisk character as a wildcard.

For example:

<?xml version="1.0" encoding="utf-8"?>
<resources xmlns:tools="http://schemas.android.com/tools"
    tools:discard="@layout/unused_1" />

For more information, see Shrink your resources.

Additional resources

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