An Android package name (the applicationId) needs at least two parts separated by dots, every part must start with a letter, and only letters, digits and underscores are allowed, for example com.novastudio.sipwell. Google Play also refuses IDs that start with com.example or run past 150 characters, and once the first build is uploaded the ID can never change. Generate one above from your company and app name, or paste any ID to check it.
What are the rules for an Android package name?
| Rule | Fails | Enforced by |
|---|---|---|
| At least two parts separated by dots | sipwell | Android |
| Every part starts with a letter | com.2fast.app | Android |
| Only letters, digits and underscores | com.nova-studio.app | Android |
| No Java keyword as a part | com.acme.class | Java and Kotlin code |
Not com.example | com.example.myapp | Google Play |
| 150 characters or fewer | a 151-character ID | Google Play |
| Lowercase | com.Nova.App works, but is discouraged | Convention |
The first three rules are Android's own, from the application ID documentation. Java keywords such as class, new or int (and true, false, null) can't be package names in code, and Android recommends keeping the code namespace the same as the application ID, so a keyword breaks the build. The Google Play limits come from the Play Console's upload checks, as of October 2026.
How do I choose a good package name?
The convention is your domain in reverse followed by the app: if you own novastudio.co.uk, use uk.co.novastudio.sipwell. No domain? com.yourname.appname is fine: the ID only has to be unique, and the Play Console tells you when you create the app if another developer already uses it. Open-source developers often use io.github.username, the reverse of their GitHub Pages address. Keep it short and lowercase, and leave out version numbers or words like "free" that may not stay true. Following the Java convention, hyphens become underscores, accents are dropped, a part that starts with a digit gets a letter in front and a keyword gets an underscore; the generator does all of this.
Can I change the package name later?
Not on Google Play. Android's documentation warns that a new application ID makes Play treat the upload as a completely different app, and the Play Console calls package names unique and permanent: they can't be deleted or reused. Before the first upload you can change it freely. People never see the ID anyway; they see the name and icon, so spend your creativity there with the app name generator and the app icon generator.
Where do I set it?
In Android Studio it is applicationId in the app module's build.gradle (keep namespace the same); in Expo it is android.package in app.json; in Flutter it is applicationId in android/app/build.gradle. The same ID goes into your signed release, so read signed APK and AAB for the Play Store next, then publishing on Google Play. Building with the APK builder? Set the package ID once for the Play Store build and every signed AAB uses it.
Frequently asked
What is an Android package name?
The package name, also called the application ID, is the unique ID of an Android app on the phone and on Google Play. It is written like a web address in reverse, for example com.novastudio.sipwell, and it appears in the app's Play Store link after id=.
Can an Android package name contain uppercase letters?
Android accepts uppercase letters and a few published apps use them, but package names are written in lowercase by convention and Google Play's upload error message asks for a lowercase first letter. Use all lowercase for a new app.
Why does Google Play say com.example is restricted?
com.example is the placeholder that Android Studio and many templates start with. Google Play refuses uploads whose package name starts with com.example, with the message that com.example is restricted, so replace it with your own name before the first upload.
Do I need to own the domain in my package name?
Nothing checks domain ownership, but the convention is a reversed domain you control so the ID stays unique. Without a domain, com.yourname.appname or io.github.yourusername.appname is fine. Google Play only refuses an ID that another developer already uses.
Can I change the package name after publishing on Google Play?
No. Google Play treats an upload with a different package name as a completely different app, and package names can't be deleted or re-used. Changing it means a new listing without the old installs, ratings and reviews.
Is what I type sent anywhere?
No. The suggestions and the checks are worked out in your browser, so the company and app names you enter never leave your device.
Build your app with AI — free to start
Describe it, sign in, and the agent builds it while you watch. Download the APK when it's ready.
Build a water reminder app ›