By default, WhatsApp will automatically download images over your cellular connection to provide you with quick access to your latest photos.
To configure automatic photo, video, or audio downloading, simply go to Settings > Media settings > Media auto-download.
Here you can choose when WhatsApp will automatically download media.
When using mobile data:
Selected media will automatically download when you are connected to your mobile data connection.
When connected to WiFi:
Selected media will automatically download when you are connected to a Wi-Fi hotspot (e.g. your home internet).
Selected media will automatically download when you are roaming.
Note: enabling roaming auto-download may result in significantly increased charges from your mobile provider as roaming data is often expensive.
Automatically downloaded images will show up in your phone's media folder.
WhatsApp Support Team