## Upgrade from Wear 2.0


This guide describes the upgrade process for Wear OS.

### Android-specific changes


Wear 2.0 encompasses multiple Android versions, from API level 25 through
API level 28.

**Note:** There is no version of Wear OS for Android 10 (API Level 29).


If your Wear OS app targets Wear OS 2.0 (API level 28), then most of the work
to upgrade is handling the platform changes from Android 9 (API level 28) to
Android 11 (API level 30).

There is no version of Wear OS for Android 10 (API Level 29), you need to handle those
changes all at once when you change your `compileSdkVersion` and
`targetSdkVersion` fields from 28 to 30.

**Note:** Even if you don't change the `compileSdkVersion` or
`targetSdkVersion` in your app, ensure that your app is
[compatible](https://developer.android.com/about/versions/11/migration#compat) with API Level 29.

### Changes specific to Wear OS


[Tiles](https://developer.android.com/training/articles/wear-tiles),
[complications](https://developer.android.com/training/wearables/watch-faces/complications),
apps, [watch faces](https://developer.android.com/training/wearables/watch-faces), and many other surfaces
exist in Wear OS 2.0. When you upgrade your app, you must revise your user interfaces
to incorporate the latest design guidelines.


Also, API level 30 includes the
[Ongoing Activity API](https://developer.android.com/reference/androidx/wear/ongoing/OngoingActivity).
An [ongoing activity](https://developer.android.com/training/wearables/ongoing-activity) lets an
ongoing notification appear on additional surfaces within the Wear OS user
interface, which lets users stay more engaged with long-running activities.

**Note:** Some features of alpha watch face APIs are available only on
devices running API level 30 or higher.

## Choose a version to start with


Most developers build a solid app that targets API level 30 and
leave the `minSdkVersion` version low enough to target the most prevalent Android
versions. For example, to enable support for Wear 2.0 devices, set your `minSdkVersion`
to 25.


If you have experience with Android development, much of that knowledge is applicable to Wear OS.
To find out what differs, read
[Wear OS versus mobile development](https://developer.android.com/training/wearables/wear-v-mobile).


**Note** : The API level 30 Wear OS emulator system image is in Developer
Preview. See the
[release notes](https://androidstudio.googleblog.com/2021/05/android-studio-arctic-fox-beta-1.html)
for the latest updates.

## Jetpack libraries for Wear OS


The [Jetpack libraries for Wear OS](https://developer.android.com/jetpack/androidx/releases/wear) are a set of
libraries that contain similar functionality to the Wearable Support library and better support
for Wear OS 3.


The Jetpack libraries for Wear OS are replacements for the Wearable Support Library and aren't
designed to be used together. The Wearable Support Library does not work on Wear OS 3.


For more information, see the blog post
[Wear OS Jetpack libraries now in stable](https://android-developers.googleblog.com/2021/09/wear-os-jetpack-libraries-now-in-stable.html).