<!--
{
  "availability" : [
    "iOS: 2.0.0 -",
    "iPadOS: 2.0.0 -",
    "macOS: 10.0.0 -",
    "tvOS: 9.0.0 -",
    "visionOS: 1.0.0 -",
    "watchOS: 2.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "BundleResources",
  "identifier" : "/documentation/BundleResources/Information-Property-List/CFBundleIdentifier",
  "metadataVersion" : "0.1.0",
  "role" : "Property List Key",
  "symbol" : {
    "kind" : "Property List Key",
    "modules" : [
      "Bundle Resources"
    ],
    "preciseIdentifier" : "plist:Information_Property_List.CFBundleIdentifier"
  },
  "title" : "CFBundleIdentifier"
}
-->

# CFBundleIdentifier

A unique identifier for a bundle.

## Discussion

A *bundle ID* uniquely identifies a single app throughout the system. The bundle ID string must contain only alphanumeric characters (A–Z, a–z, and 0–9), hyphens (-), and periods (.). Typically, you use a reverse-DNS format for bundle ID strings. Bundle IDs are case-insensitive.

The operating system uses the bundle ID to identify the app when applying specified preferences. Similarly, <doc://com.apple.documentation/documentation/coreservices/launch_services> uses the bundle ID to locate an app capable of opening a particular file. The bundle ID also validates an app’s signature.

> Important:
> The bundle ID in the information property list must match the bundle ID you enter in App Store Connect. After you upload a build to App Store Connect, you can’t change the bundle ID or delete the associated explicit App ID in your developer account.

### watchOS Apps with Companion iOS App Considerations

For watchOS apps that have a companion iOS app in the same project, the embedded WatchKit app and WatchKit extension targets must have the same bundle ID prefix as the iOS app. The WatchKit app must have the format `[Bundle ID].watchkitapp`, and the WatchKit extension must have the format `[Bundle ID].watchkitextension`.

If you change the iOS app’s bundle ID, also change the WatchKit app’s  [`WKCompanionAppBundleIdentifier`](/documentation/BundleResources/Information-Property-List/WKCompanionAppBundleIdentifier) key and the WatchKit extension’s [`WKAppBundleIdentifier`](/documentation/BundleResources/Information-Property-List/WKAppBundleIdentifier) key to match.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)