bundletool

bundletool is the underlying tool that Android Studio, the Android Gradle plugin, and Google Play use to build an Android App Bundle. bundletool can convert an app bundle into the various APKs that are deployed to devices.

Android SDK Bundles (ASBs) and their APKs are built with bundletool. It is also available as a command-line tool, so you can build app bundles and SDK bundles yourself and re-create Google Play's server-side build of your app's APKs or your runtime-enabled SDK's APKs.

Download `bundletool`

If you haven't already, download bundletool from the GitHub repository.

Build and test an app bundle

You can use Android Studio or the bundletool command-line tool to build your Android App Bundle and then test generating APKs from this app bundle.

Build an app bundle

Use Android Studio and the Android Gradle plugin to build and sign an Android App Bundle. However, if using the IDE is not an option—for example, because you are using a continuous build server—you can also build your app bundle from the command line and sign it using jarsigner.

For more information about building app bundles with bundletool, see Build an app bundle using bundletool.

Generate a set of APKs from your app bundle

After you build your Android App Bundle, test how Google Play uses it to generate APKs and how those APKs behave when deployed to a device.

There are two ways you can test your app bundle:

Use the bundletool command-line tool locally.
Upload your bundle to the Play Console through Google Play by using a test track.

This section explains how to use bundletool to test your app bundle locally.

When bundletool generates APKs from your app bundle, it includes the generated APKs in a container called an APK set archive, which uses the .apks file extension. To generate an APK set for all device configurations your app supports from your app bundle, use the bundletool build-apks command, as shown:

bundletool build-apks --bundle=/MyApp/my_app.aab --output=/MyApp/my_app.apks

If you want to deploy the APKs to a device, you also need to include your app's signing information, as shown in the following command. If you don't specify signing information, bundletool attempts to sign your APKs with a debug key for you.

bundletool build-apks --bundle=/MyApp/my_app.aab --output=/MyApp/my_app.apks
--ks=/MyApp/keystore.jks
--ks-pass=file:/MyApp/keystore.pwd
--ks-key-alias=MyKeyAlias
--key-pass=file:/MyApp/key.pwd

The following table describes the various flags and options you can set when using the bundletool build-apks command in greater detail:

Table 1. Options for the bundletool build-apks command

Flag	Description
`--bundle=path`	(Required) Specifies the path to the app bundle you built using Android Studio. To learn more, read Build your project.
`--output=path`	(Required) Specifies the name of the output `.apks` file, which contains all the APK artifacts for your app. To test the artifacts in this file on a device, follow the steps in the section about how to deploy APKs to a connected device.
`--overwrite`	Overwrites any existing output file with the path you specify using the `--output` option. If you don't include this flag and the output file already exists, you get a build error.
`--aapt2=path`	Specifies a custom path to AAPT2. By default, `bundletool` includes its own version of AAPT2.
`--ks=path`	(Optional) Specifies the path to the deployment keystore used to sign the APKs. If you don't include this flag, `bundletool` attempts to sign your APKs with a debug signing key.
`--ks-pass=pass:password` or `--ks-pass=file:/path/to/file`	Specifies your keystore password. If you specify a password in plain text, qualify it with `pass:`. If you pass the path to a file that contains the password, qualify it with `file:`. If you specify a keystore using the `--ks` flag without specifying `--ks-pass`, `bundletool` prompts you for a password from the command line.
`--ks-key-alias=alias`	Specifies the alias of the signing key you want to use.
`--key-pass=pass:password` or `--key-pass=file:/path/to/file`	Specifies the password for the signing key. If you specify a password in plain text, qualify it with `pass:`. If you pass the path to a file that contains the password, qualify it with `file:`. If this password is identical to the one for the keystore itself, you can omit this flag.
`--connected-device`	Instructs `bundletool` to build APKs that target the configuration of a connected device. If you don't include this flag, `bundletool` generates APKs for all device configurations your app supports.
`--device-id=serial-number`	If you have more than one connected device, use this flag to specify the serial ID of the device to which you want to deploy your app.
`--device-spec=spec_json`	Provides a path to a `.json` file that specifies the device configuration you want to target. To learn more, go to the section about how to Generate and use device specification JSON files.
`--mode=universal`	Sets the mode to `universal`. Use this option if you want `bundletool` to build a single APK that includes all of your app's code and resources, so that the APK is compatible with all device configurations your app supports. Note: `bundletool` includes only feature modules that specify `<dist:fusing dist:include="true"/>` in their manifest in a universal APK. To learn more, read about the feature module manifest. Keep in mind, these APKs are larger than those optimized for a particular device configuration. However, they're easier to share with internal testers who, for example, want to test your app on multiple device configurations.
`--local-testing`	Enables your app bundle for local testing. Local testing allows for quick, iterative testing cycles without the need to upload to Google Play servers. For an example of how to test module installation using the `--local-testing` flag, see Locally test module installs.

Deploy APKs to a connected device

After you generate a set of APKs, bundletool can deploy the right combination of APKs from that set to a connected device.

For example, if you have a connected device running Android 5.0 (API level 21) or higher, bundletool pushes the base APK, feature module APKs, and configuration APKs required to run your app on that device. Alternatively, if your connected device is running Android 4.4 (API level 20) or lower, bundletool searches for a compatible multi-APK to deploy to your device.

To deploy your app from an APK set, use the install-apks command and specify the path of the APK set using the --apks=/path/to/apks flag, as shown in the following command. If you have multiple devices connected, specify a target device by adding the --device-id=serial-id flag.

bundletool install-apks --apks=/MyApp/my_app.apks

Generate a device-specific set of APKs

If you don't want to build a set of APKs for all device configurations your app supports, you can build APKs that target only the configuration of a connected device using the --connected-device option, as shown in the following command. If you have multiple devices connected, specify a target device by including the --device-id=serial-id flag.

bundletool build-apks --connected-device
--bundle=/MyApp/my_app.aab --output=/MyApp/my_app.apks

Generate and use device specification JSON files

bundletool can generate an APK set that targets a device configuration specified by a JSON file. To first generate a JSON file for a connected device, run the following command:

bundletool get-device-spec --output=/tmp/device-spec.json

bundletool creates a JSON file for your device in the tool's directory. You can then pass the file to bundletool to generate a set of APKs that target only the configuration described in that JSON file, as follows:

bundletool build-apks --device-spec=/MyApp/pixel2.json
--bundle=/MyApp/my_app.aab --output=/MyApp/my_app.apks

Manually create a device specification JSON

If you don't have access to the device for which you want to build a targeted APK set—for example, if you want to try your app with a device you don't have on hand—you can manually create a JSON file using the following format:

{
  "supportedAbis": ["arm64-v8a", "armeabi-v7a"],
  "supportedLocales": ["en", "fr"],
  "screenDensity": 640,
  "sdkVersion": 27
}

You can then pass this JSON to the bundle extract-apks command, as described in the previous section.

Extract device-specific APKs from an existing APK set

If you have an existing APK set and you want to extract from it a subset of APKs that target a specific device configuration, you can use the extract-apks command and specify a device specification JSON, as follows:

bundletool extract-apks
--apks=/MyApp/my_existing_APK_set.apks
--output-dir=/MyApp/my_pixel2_APK_set.apks
--device-spec=/MyApp/bundletool/pixel2.json

Measure the estimated download sizes of APKs in an APK set

To measure the estimated download sizes of APKs in an APK set as they would be served compressed over the wire, use the get-size total command:

bundletool get-size total --apks=/MyApp/my_app.apks

You can modify the behavior of the get-size total command using the following flags:

Table 2. Options for the get-size total command

Flag	Description
`--apks=path`	(Required) Specifies the path to the existing APK set file whose download size is being measured.
`--device-spec=path`	Specifies the path to the device spec file (from `get-device-spec` or constructed manually) to use for matching. You can specify a partial path to evaluate a set of configurations.
`--dimensions=dimensions`	Specifies the dimensions used when computing the size estimates. Accepts a comma-separated list of: `SDK`, `ABI`, `SCREEN_DENSITY`, and `LANGUAGE`. To measure across all dimensions, specify `ALL`.
`--instant`	Measures the download size of the instant-enabled APKs instead of the installable APKs. By default, `bundletool` measures the installable APK download sizes.
`--modules=modules`	Specifies a comma-separated list of modules in the APK set to consider in the measurement. The `bundletool` command automatically includes any dependent modules for the specified set. By default, the command measures the download size of all modules installed during the first download.

Build an app bundle with an SDK bundle dependency (experimental)

You can build your Android App Bundle with an Android SDK Bundle (ASB) dependency from the command line and sign it using jarsigner.

Each app bundle module includes a Module Protocol Buffer (.pb) file: runtime_enabled_sdk_config.pb. This file contains the list of SDKs that an app bundle module depends on. For the full definition of this file, see the runtime_enabled_sdk_config.proto file.

To build an app bundle with an SDK bundle dependency, follow the steps in the section about building an app bundle using bundletool and add a runtime_enabled_sdk_config.pb file to each app module's zip file with compiled code and resources.

Some notable fields in the runtime_enabled_sdk_config.pb file:

Certificate digest: the SHA-256 digest of the certificate for the key used to sign the SDK's APKs. This corresponds to the certificate in the SdkMetadata.pb file in the Android SDK Archive format.
Resources Package ID: the package ID that all resources in this SDK are remapped to when generating APKs for embedding the SDK into the app. This enables backward compatibility.

An SDK can appear only in one module. If multiple modules depend on the same SDK, this dependency should be deduplicated and moved to the base module. Different modules can't depend on different versions of the SDK.

Generate APKs from an app bundle with an SDK bundle dependency

To generate APKs from your app bundle, follow the steps in the section about generating a set of APKs from your app bundle or the section about generating a device-specific set of APKs and provide the bundletool build-apks command with the SDKs that the app depends on. These SDKs can be provided in SDK bundle format or SDK Archive format.

You can provide the SDKs as SDK bundles by adding the --sdk-bundles flag, as follows:

bundletool build-apks --bundle=app.aab --sdk-bundles=sdk1.asb,sdk2.asb \
    --output=app.apks

You can provide the SDKs as SDK archives by adding the --sdk-archives flag, as follows:

bundletool build-apks --bundle=app.aab --sdk-archives=sdk1.asar,sdk2.asar \
    --output=app.apks

Build and test an SDK bundle (experimental)

You can use bundletool to build an ASB and test generating the files needed for installation and distribution.

Build an SDK bundle

You can build your ASB from the command line and sign it using jarsigner.

To build an SDK bundle, follow these steps:

Generate the SDK bundle's manifest and resources in proto format by following the same steps as for an app bundle.
Package your SDK's compiled code and resources into a base zip file, as you would with an app module.
Generate an SdkModulesConfig.pb.json file and an SdkBundleConfig.pb.json file, matching the format described in the Android SDK Bundle specification.
Build your ASB using the bundletool build-sdk-bundle command, as follows:

bundletool build-sdk-bundle --sdk-bundle-config=SdkBundleConfig.pb.json \
    --sdk-modules-config=SdkModulesConfig.pb.json \
    --modules=base.zip --output=sdk.asb

The following table describes the various flags and options you can set when using the bundletool build-sdk-bundle command in greater detail.

Table 3. Options for the bundletool build-sdk-bundle command

Flag	Description
`--modules`	(Required) The module file that you want to build the final ASB from.
`--output`	(Required) The path to where you want the ASB to be built.
`--sdk-modules-config`	(Required) The path to a JSON file that describes the configuration of the SDK modules. To learn how to format the JSON file, see the Android SDK Bundle specification section.
`--sdk-bundle-config`	The path to a JSON file that describes the configuration of the SDK bundle. To learn how to format the JSON file, see the Android SDK Bundle specification section.
`--metadata-file`	The file to include metadata in for the ASB. The format of the flag value is `<bundle-path>:<physical-file>`, where `<bundle-path>` denotes the file location inside the SDK bundle's metadata directory and `<physical-file>` is an existing file that contains the raw data to be stored. The flag can be repeated.
`--overwrite`	If set, this option overwrites any previous existing output.

Generate APKs from an SDK bundle

After you build your ASB, you can test an SDK bundle locally by generating its APKs using the bundletool build-sdk-apks command, as shown in the following code:

bundletool build-sdk-apks --sdk-bundle=sdk.asb --output=sdk.apks

When bundletool generates APKs from your SDK bundle, the tool includes the APKS in a container called an APK set archive, which uses the .apks file extension. bundletool generates a single standalone APK from the SDK bundle that targets all device configurations.

If you want to deploy the ASB to a device, you need to also include your app's signing information, as shown in the following command:

bundletool build-sdk-apks --sdk-bundle=sdk.asb --output=sdk.apks \
    --ks=keystore.jks \
    --ks-pass=file:/keystore.pwd \
    --ks-key-alias=KeyAlias \
    --key-pass=file:/key.pwd

The following table describes the various flags and options you can set when using the bundletool build-sdk-apks command in greater detail.

Table 4. Options for the bundletool build-sdk-apks command

Flag	Description
`--sdk-bundle`	(Required) The path to the SDK bundle. Must have the extension `.asb`.
`--output`	(Required) By default, the path where you want the APK set archive to be created. Alternatively, if you use `--output-format=DIRECTORY`, this is the path to the directory where you want generated APKs to be stored.
`--ks`	The path to the keystore that you want to use to sign the generated APKs.
`--ks-key-alias`	The alias of the key to use in the keystore to sign the generated APKs.
`--key-pass`	The password of the key in the keystore to use to sign the generated APKs. If you pass the password in clear text, you must prefix the value with `pass:`. For example, `pass:qwerty`. If the password is the first line of a file, you must prefix the value with `file:`. For example, `file:/tmp/myPassword.txt`. If this flag isn't set, the keystore password is tried. If that fails, the command-line terminal prompts you for a password.
`--ks-pass`	The password of the keystore to use to sign the generated APKs. If you pass the password in clear text, you must prefix the value with `pass:`. For example, `pass:qwerty`. If the password is the first line of a file, you must prefix the value with `file:`. For example `file:/tmp/myPassword.txt`. If this flag isn't set, the command-line terminal prompts you for a password.
`--aapt2`	The path to the AAPT2 binary to use.
`--output-format`	The output format for generated APKs. By default, this option is set to `APK_SET`, which outputs APKs into the APK set archive that is created. If set to `DIRECTORY`, it outputs APKs into the directory specified by `--output`.
`--verbose`	If set, this option prints extra information about the command execution in the standard output.
`--version-code`	The SDK version code. This is the version code used by the Android platform to install the APK, not the SDK version. This option can be set to an arbitrary value. If not set, it defaults to 0.
`--overwrite`	If set, this option overwrites any previous existing output.

Deploy, extract, and measure the size of SDK APKs

You can follow the same steps used for apps to deploy APKs to a connected device, extract device-specific APKs from an existing APK set, and measure the estimated download sizes of APKs in an APK set.

Generate an SDK Archive from an SDK bundle

After you upload your ASB to your distribution channel, for example Google Play, the ASB is transformed into an Android SDK Archive (.asar) for distribution to app developers through Maven. For more details about the format, see the section about SDK Archive format specification.

After you build your ASB, you can test the generation of an Android SDK Archive locally using the bundletool build-sdk-asar command, as shown in the following code:

bundletool build-sdk-asar --sdk-bundle=sdk.asb --output=sdk.asar \
    --apk-signing-key-certificate=keycert.txt

The following table describes the various flags and options you can set when using the bundletool build-sdk-asar command in greater detail.

Table 5. Options for the bundletool build-sdk-asar command

Flag	Description
`--apk-signing-key-certificate`	(Required) The path to the SDK APK signing certificate. This is the certificate corresponding to the key that you used to sign the APKs in the `build-sdk-apks` command.
`--output`	(Required) The path where you want the `.asar` file to be created.
`--sdk-bundle`	(Required) The path to the SDK bundle. Must have the extension `.asb`.
`--overwrite`	If set, this option overwrites any previous existing output.

Runtime-enabled SDK formats (experimental)

Runtime-enabled SDKs introduce two Android file formats:

The Android SDK Bundle (.asb), used to publish the runtime-enabled SDK to app stores.
The Android SDK Archive (.asar), used to distribute the runtime-enabled SDK on Maven.

The Android SDK Bundle format

An SDK Bundle is a publishing format for runtime-enabled SDKs. It contains all the SDK code and resources, including the code from any libraries the SDK depends on. It doesn't include the code and resources of other runtime-enabled SDKs that the SDK depends on.

An Android SDK Bundle (ASB) is a signed zip file with the extension .asb. The SDK code and resources are organized in it similarly to what you would find in an APK. An ASB also contains several configuration files that help generate the installable APKs.

**Figure 1.** The contents of an Android SDK Bundle.

The following list describes some of the ASB files in more detail:

SdkBundleConfig.pb: A configuration file in proto format, containing the list of runtime-enabled SDKs that your SDK depends on. For the full definition, see the sdk_bundle_config.proto file.
modules.resm: A zip file containing all the data needed to generate the APKs from the SDK.
SdkModulesConfig.pb: A configuration file in proto format. This file contains the SDK name, version, and class name of the SDK entry point for the framework (SandboxedSdkProvider). For the full definition, see the sdk_modules_config.proto file.
base/: The single module containing the SDK code and resources.
- manifest/: The manifest of the SDK in proto format.
- dex/: The compiled code in DEX format. Multiple DEX files can be provided.
- res/, lib/, assets/: These directories are identical to those in a typical APK. Paths in these directories are preserved when generating the SDK's APKs.
- root/: This directory stores files that are later relocated to the root of the SDK APKs. For example, it might include Java-based resources that your SDK loads using the Class.getResource() method. Paths within this directory are also preserved.
- BUNDLE-METADATA: This directory includes metadata files that contain information useful for tools or app stores. Such metadata files might include ProGuard mappings and the complete list of your SDK's DEX files. Files in this directory are not packaged into your SDK's APKs.

The Android SDK Archive format

An Android SDK Archive is the distribution format of a runtime-enabled SDK on Maven. It's a zip file with the file extension .asar. The file contains all information that is needed by the app build tools to generate an Android App Bundle that depends on your runtime-enabled SDK.

**Figure 2.** The contents of an Android SDK Archive Bundle.

The following list describes some of the Android SDK Archive files in more detail:

SdkMetadata.pb: A configuration file in proto format containing the SDK name, version, and the certificate digest for the key used to sign the APKs generated for this SDK. For the full definition, see the sdk_metadata.proto file.
modules.resm: A zip file containing all the data needed to generate the APKs from the SDK. This is the same as the .resm file in the Android SDK Bundle.
AndroidManifest.xml: The manifest file of the SDK in text XML format.

Additional resources

To learn more about using bundletool, watch App Bundles: Testing bundles with bundletool and the Play Console.