Apple Sign In button not localizing to German despite device language and app support

[zjamshidi]

Expected Behavior
"Sign in with Apple" button should localize to "Mit Apple anmelden" in FirebaseUI Auth when device/iPhone is German or UserDefaults.standard.set(["de"], forKey: "AppleLanguages") is called (and synchronized). Other providers localize correctly; Apple's native ASAuthorizationAppleIDButton supports de-DE.

Actual Behavior
Button stays "Sign in with Apple" (English) despite:

• iPhone language: German (Settings > General > Language & Region)
• UserDefaults.set(["de"], forKey: "AppleLanguages") + UserDefaults.standard.synchronize()
• Sign-in dialogs: German ✓
• Other buttons (Google/Email): German ✓
• Info.plist: ende ✓

Am I missing something? Is it expected?

[russellwheatley]

Hi @zjamshidi - could you provide further information. What version are you using? Are you using SwiftUI or UIkit version of FirebaseUI Auth library?

[zjamshidi]

Hi @russellwheatley. I'm using the UIKit version. Here are my dependencies:

  pod 'Firebase/Auth', '~> 12.4.0'
  pod 'FirebaseUI/Auth', '~> 15.1.0'

I have set the AppleLanguages when the language is selected. I also set Auth.auth().languageCode when the app launches.

As a side note, is it possible to change the SDK's language at runtime without restarting the app?

[russellwheatley]

@zjamshidi - I'm afraid we don't support the UIKit version anymore. In fact, it has been completely removed from the repository. We have a new version out which is written for SwiftUI, here is the documentation if you want to take a look: https://github.com/firebase/FirebaseUI-iOS/blob/main/FirebaseSwiftUI/README.md

As another thing to note - cocoapods will become read-only from December 2026 🙏

[zjamshidi]

At the moment, I can’t migrate to SwiftUI. I updated the app to follow the device’s locale, so there is no custom language selector anymore. However, the Apple Sign In button is still shown in English.

Generally speaking, shouldn’t it appear in German when the device language is set to German? Am I missing something?

[russellwheatley]

Generally speaking - Yes, it probably should be I believe. The only thing I can think of at the moment is to fork the repo and go back to the last version of the previous release for the old FirebaseUI Auth and resolve the issue there, and point to your fork from your Podfile.