ChromeOS devices, such as Chromebooks, support the Google Play Store and Android apps. This article assumes you have an existing Android app designed for phones or tablets that you want to optimize for Chromebooks. To learn the basics of building Android apps, see[Build your first Android app](https://developer.android.com/training/basics/firstapp).

## Update your app's manifest file

To get started, update your manifest file to account for some key hardware and software differences between Chromebooks and other devices running Android.

As of ChromeOS version M53, all Android apps that don't explicitly require the[`android.hardware.touchscreen`](https://developer.android.com/guide/topics/manifest/uses-feature-element#touchscreen-hw-features)feature also work on ChromeOS devices that support the`android.hardware.faketouch`feature. However, to ensure your app works on all Chromebooks, update your manifest file so that the`android.hardware.touchscreen`feature is not required, as shown in the following example.  

```xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          ... >
    <!-- Some Chromebooks don't support touch. Although not essential,
         it's a good idea to explicitly include this declaration. -->
    <uses-feature android:name="android.hardware.touchscreen"
                  android:required="false" />
</manifest>
```
| **Note:** Removing the requirement for touch input means you need to review your app's support for[mouse and keyboard interactions](https://developer.android.com/develop/ui/compose/touch-input).

Different hardware devices come equipped with different sets of sensors, and Chromebooks might not have all the sensors found in Android handheld devices, such as GPS and accelerometers. However, in some cases the functionality of a sensor is provided in another way. For example, Chromebooks might not have GPS sensors, but they provide location data based on Wi-Fi connections. See the[sensors overview](https://developer.android.com/guide/topics/sensors/sensors_overview)to learn more about the sensors that the Android platform supports.

If you want your app to run on Chromebooks regardless of sensor availability, update your manifest file so that no sensors are required.
| **Note:** If you don't require a particular sensor for your app but still use measurements from the sensor when it's available, make sure you dynamically check for the sensor's availability before trying to gather information from it.

Some software features are not supported on Chromebooks. For example, apps that provide custom IMEs, app widgets, live wallpapers, and app launchers aren't supported and can't be installed on Chromebooks. For a complete list of software features that aren't supported on Chromebooks, see[incompatible software features](https://developer.android.com/topic/arc/manifest#incompat-software-features).

## Update your target SDK

Update your app's[`targetSdkVersion`](https://developer.android.com/reference/android/R.attr#targetSdkVersion)attribute to the latest API level available to take advantage of all the improvements in the Android platform. Review the improvements in the Android platform throughout different[versions](https://developer.android.com/about/versions).

## Check for networking requirements

Chromebooks run the entire Android OS in a container, similar to Docker or LXC. This means that Android doesn't have direct access to the system's LAN interface. Instead, IPv4 traffic passes through an internal layer of network address translation (NAT), and IPv6 unicast traffic is routed through an extra hop.

Outbound unicast connections from an Android app to the internet mostly work as-is. In general, inbound connections are blocked. Multicast or broadcast packets from Android are not forwarded to the LAN through the firewall.

As an exception to the multicast restriction, ChromeOS runs a service that forwards mDNS traffic between Android and the LAN interface, so the standard[network service discovery](https://developer.android.com/training/connect-devices-wirelessly/nsd)APIs are the recommended way to discover other devices on the LAN segment. After finding a device on the LAN, an Android app can use standard TCP or UDP unicast sockets to communicate with it.

IPv4 connections originating from Android use the ChromeOS host's IPv4 address. Internally, the Android app sees a private IPv4 address assigned to the network interface. IPv6 connections originating from Android use a different address from the ChromeOS host, because the Android container has a dedicated public IPv6 address.

## Use cloud and local storage effectively

Chromebooks let users easily migrate from one device to another. If a user stops using one Chromebook and starts using another, they only have to sign in, and all of their apps appear.

Because of this feature, back up your app's data to the cloud to enable syncing across devices. However, don't depend on an internet connection for your app to operate normally. Instead, save the user's work locally when the device is offline and sync to the cloud once the device is back online.

Chromebooks can also be shared among a large number of people, such as in schools. Since local storage is not infinite, entire accounts---together with their storage---can be removed from the device at any point. For educational settings, it's a good idea to keep this scenario in mind.

## Develop new test cases for your app

To develop test cases for your app, first make sure that you specify the proper manifest flags. In particular, consider setting[screenOrientation](https://developer.android.com/reference/android/R.attr#screenOrientation)to`unspecified`. If you want to specify a landscape orientation, consider using`sensorLandscape`to make sure that the experience on a tablet is optimal.

If you have special size or orientation needs for desktop environments, consider adding meta tags as size or orientation hints. To include size and orientation on phones, specify layout[defaultHeight](https://developer.android.com/reference/android/R.attr#defaultHeight),[defaultWidth](https://developer.android.com/reference/android/R.attr#defaultWidth), or[minHeight](https://developer.android.com/reference/android/R.attr#minHeight)attributes instead.

If you are interested in specific input device handling for specific device categories, specify`android.hardware.type.pc`to disable input compatibility mode.

If you are using any kind of networking, make sure that the app can reconnect to the network after a connection problem is resolved or the device wakes from sleep mode.

We recommend checking the list of[test cases for Android apps on Chrome OS](https://developer.android.com/topic/arc/tests), which you can use in your test plan. The test cases cover common scenarios that Android apps should be prepared for if they are expected to run on ChromeOS devices.

### Multi-window and orientation changes

ChromeOS's multi-window environment can make state persistence and recall issues more obvious. Use[`ViewModel`](https://developer.android.com/topic/libraries/architecture/viewmodel)to save and restore your state when appropriate.

To test state persistence, minimize your app for some time, start another resource intensive process, and restore your app to confirm that it returns to the state you left it in.

Test window resizing by pressing the full screen key (F4), maximizing, and restoring. To test free resizing, first enable it in the developer options, and then check that your app smoothly resizes without crashing.

If your ChromeOS device supports it, change from laptop to tablet mode to check whether everything works as expected. Rotate the device once in tablet mode to test orientation changes, then transition back to laptop mode. Repeat this step a few times.

Make sure that the top bar is not breaking your app by offsetting UI elements or location-based touch input. For ChromeOS devices, make sure that your app doesn't place important information in the status bar area.

If you are using the camera or another hardware feature, like the pen, make sure that it behaves properly when performing the window and device changes outlined previously.