Samsung
Set Apps to Always Use Mobile Data auf Samsung
An app burning through your mobile data plan while your phone shows a full WLAN signal usually points to one specific toggle in One UI: Mobile data only apps. This setting lets you mark individual apps so they ignore any WLAN network and always route their traffic through the mobile connection instead.
Samsung built this for apps where speed or connection stability matters more than data savings, for example live streaming tools or navigation apps that struggle with weak or restricted WLAN networks. Once enabled for an app, that app stops using WLAN entirely, even on a fast home network, and pulls exclusively from your mobile data allowance.
You manage this list under Settings ➔ Connections ➔ Data usage ➔ Mobile data only apps. From there you can enable or disable the feature overall and turn it on or off for each app individually.
If your data usage climbs unexpectedly or an app feels slow despite good WLAN, check this list first. Turning an app off here returns it to normal behavior, using WLAN whenever available and only falling back to mobile data when needed.