How can I set up certain apps to use mobile data when wifi is not available

[GeoA13]

I have an A13 Samsung. I want all the apps installed in my phone to access the internet only through wifi. When wifi is not available I want only one app (WhatsApp) to use mobile data. I'm trying to do that but I can't do it. If I go to Settings>Connections>Data usage and click on “Mobile data” all the apps will use mobile data but I do no want that. I want only one app, that is, WhatsApp to use mobile data (when wifi is not available) so I can send and receive messages.

[Neo001]

There is no direct way, but you can try the following -

Enable Data saver in Setting> Connection > Data usage.

Next disallow all the apps to access data when Data saver is on, except WhatsApp (and few other apps like system apps).

[AndrewL]

@GeoA13: You could try heading to Settings > Connections > Data usage > Data Saver > On > Allowed to use data while Data Saver is on > WhatsApp. Now, head to Settings > Connections > Wi-Fi > Tap the 3 dots in the top right > Advanced > Switch to Mobile Data > On. Let me know if this helps. 

[GeoA13]

How do we disallow all the apps to use mobile data except WhatsApp?

[GeoA13]

You said: “Allowed to use data while Data Saver is on > WhatsApp.”

Could you please tell me how do I select WhatsApp to use mobile data while Data Saver is On?