Samsung
App Download Preference (Wi-Fi Only) auf Samsung
By default, the Play Store downloads and updates apps over whatever connection is available, including mobile data. This behavior is controlled by a Play Store setting called App download preference, not by a system-wide Android option.
If you never touched this setting, your phone falls back to mobile data automatically whenever Wi-Fi drops, which explains sudden data usage spikes right after app updates roll out.
To limit downloads to Wi-Fi only, open Play Store ➔ tap your Google account icon ➔ Settings ➔ Network preferences ➔ App download preference. Pick the option that restricts downloads to Wi-Fi and confirm with Done.
This setting covers both new installs and automatic updates queued inside the Play Store. It has no effect on files downloaded through a browser or a third-party app store.
If you only want to pause automatic updates rather than block mobile data entirely, turning off auto-updates in the same Network preferences menu is a lighter option.
Keep in mind that Wi-Fi only downloads wait until you connect to a wireless network, which can delay security patches if you rarely use Wi-Fi.