Introduction

If you want to clear everything your app stored in NSUserDefaults, the cleanest solution is to remove the app’s persistent domain rather than deleting keys one by one. That resets the defaults for your app in a single operation and is usually more reliable than manually iterating through every stored key.

Remove the App’s Persistent Domain

In modern Swift using UserDefaults, the usual pattern is:

if let bundleID = Bundle.main.bundleIdentifier {
    UserDefaults.standard.removePersistentDomain(forName: bundleID)
}

This removes the app’s stored defaults domain, which is effectively the closest thing to “delete all keys.”

It is usually better than enumerating keys yourself because it targets the whole defaults domain directly.

Delete Individual Keys Only When You Need Selective Reset

If you need to preserve some settings but remove others, then iterate or remove known keys explicitly.

let defaults = UserDefaults.standard
defaults.removeObject(forKey: "authToken")
defaults.removeObject(forKey: "lastSyncDate")

That is the right tool for partial cleanup, but not for a full reset.

Understand What You Are Actually Clearing

UserDefaults is meant for lightweight preference-like storage. Clearing it resets values your app stored there, such as:

• flags
• small settings
• cached preference values

It does not delete:

• Keychain items
• files in Documents or Caches
• database contents
• server-side user state

That distinction matters because some “log out and reset” flows need more than just clearing defaults.

Be Careful with Registration Defaults

If your app registers default values with register(defaults:), those are not the same as persisted keys. Removing the persistent domain clears stored values, but registered defaults may still appear when read afterward because they are part of the in-memory fallback behavior.

That surprises people who expect the app to return nil for every key after a reset.

Common Pitfalls

• Iterating through keys manually when removing the persistent domain would have been simpler.
• Assuming that clearing UserDefaults also clears Keychain, files, or other app storage.
• Forgetting that registered defaults can still provide fallback values after persistent data is removed.
• Resetting all defaults when the real requirement was only to clear a subset of keys.
• Running a full defaults wipe in code paths where preserving some user preferences matters.

Summary

• To clear everything in app defaults, remove the app’s persistent domain.
• Use key-by-key removal only when you need selective cleanup.
• 'UserDefaults reset affects stored preferences, not all app data.'
• Registered defaults can still appear after a full defaults wipe.
• Treat a defaults reset as part of a broader app-state design, not as a universal data purge.