Android App Bundle
App Technology

Android App Bundle (AAB) — Here Is What You Need to Know!

Isn’t it fascinating to see how there are hundreds of different specifications, architecture, screen resolutions for Android phones, and still, the same applications work on all of them? It all began from designing separate Android Packages (APKs) for different devices. It was simplified further to create a universal APK with compiled code and resources specified for every language, processor, and architecture.

Back in 2018, Google introduced the Android App Bundle — a new way to upload applications on Google Play Store. Now, from August 2021, all new applications must use this format. If you aren’t an app developer, this change may not be evident to you, but the Android App Bundle will certainly bring several modifications for you too. But first, let us know more about these android app bundles.

What are Android App Bundles?

Android App Bundle (.AAB) is an application publishing format that consists of all the resources and assets that you need to run an application, along with a lot of additional files.

The .AAB file format allows the developers to package their applications in a bundle file with everything that the users will need to install and use the applications in every supported region. Once uploaded to Google Play Store, Google turns it into the traditional .APK format with all assets and settings required by different users.

There is no alteration in the way applications are installed and used, only in how they are uploaded.

Advantages of Android App Bundle

This new publishing format offers several benefits such as

Small app sizes: App size has been a major barrier to app installation and retention. Without writing extra code or using add-on tools, Android app bundles are capable of reducing the application sizes significantly. Several popular applications have already adopted this feature and reduced their sizes by up to 50%.

For example – Here are some well-known applications whose app sizes have reduced dramatically after adopting the .AAB format.

Size Reduced By (%)



RV AppStudios














Ola Cabs





Efficient Releases: Developers can now save a lot of time and effort required to build, sign, upload, and manage several versions of the same application on the Google Play Store. They only need to build one package compiling all the codes, resources, and native libraries for the application.

Dynamic Feature Modules: This is a very interesting take on application installation. Dynamic feature modules allow users to download the code as per demand. For example, an application has two main features like video editing and file sharing. If the users are not showing interest in the file sharing feature, it can be segregated as a separate module and mentioned in its Gradle file. While generating a dynamic split APK, Google Play Store will automatically create a separate APK file for the dynamic module and deliver it as per the requirement, not to all users.

Dynamic Delivery: Google Play Store will now use a dynamic delivery process to deliver the APKs to the users. Instead of overcrowding your network with unnecessary information, you would always want to keep only as much as you need. Dynamic delivery works in a similar pattern, feeding the users as per their needs.

For example, let’s say you have a particular architecture of hardware, screen density, and software language set on your device – your system specifications. Dynamic delivery is the customized service that sends out resources depending on your device’s specifications to run the application smoothly. Developers can also use this conditional delivery feature to make their application compatible in different countries, across device types, even those with low SDK versions.

Faster App Engineering: Android App Bundle supports modular app development. This implies that developers can build, design, debug, and test independent feature modules for their applications and later on, add those to the main app when finished. With fewer merge conflicts and hindrances, companies can skip having an entire engineering team focused on the same app.

Rapid Build Times: As the build systems are now optimized for modular applications, they are faster to build. Developers can instantly code, design, and test their applications instead of waiting around.

Trial Experiences on Google Play Store: Developers can now make their applications available for trial experiences on Google Play Store without even installing them. There is a dedicated Try Now button on the Google Play app and a web link to allow using the apps without installation.

Disadvantages of Android App Bundle

With all the great modifications coming, there are certain disadvantages to using AABs, mostly for the developers. Two of the prime concerns to note are:

Handing over signing keys to app stores: For applications to run on android devices, developers have to digitally sign them. The digital signature is verified every time the application is updated. With AAB files, Google is creating the APK format, which means that Google is authorized to sign all the applications. For this, developers have to let Google assign a key or provide their signing key to Google.

Signing keys are intrinsic to app security, so developers are a tad reluctant to shift to the AAB format. Later, Google also announced Code Transparency to allow the developers to create a secondary private key for their personal usage. These concerns of developers are valid as the Android App Bundle will further give Google more control over everything in the Android domain.

Hassles in sideloading: Sideloading an APK is way easier than sideloading an AAB. There are third-party installer applications to carry out this process. Google has also launched an open-source software, Bundletool, that can make APKs from your preferred choice of app bundles.

So, What Has Changed in August 2021?

Based on the above discussion, here’s a quick summary of all that has changed in August 2021.

  • Google Play Store is replacing the APK format with the AAB format.
  • Instant app Zip can provide an instant experience with the AAB.
  • Play Asset Delivery (PAD) and Play Feature Delivery (PFD) will replace the Expansion files (OBBs).

Currently, over 1 million applications have already migrated to AABs. This is definitely the beginning of a new chapter for Android APKs with its own set of advantages and disadvantages.

But developers should brace themselves for this change as all new applications on Google Play Store will follow the AAB format, using Play Asset Delivery or Play Feature Delivery to deliver assets exceeding a download size of 150 MB.

Remember, AAB is only the publishing format – APK is the packaging format that ultimately gets installed on your android device.

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