If you want to avoid this problem, then for this you have to make a slight change in the setting. Let us now tell you how you can save WhatsApp media files in your Android and iPhone from being saved in the phone’s gallery or say by reducing the phone’s storage.
for android users
1) First open the WhatsApp app.
2) After this click on the three dots appearing on the right side.
3) Here you will get the option of Settings.
4) After clicking on Settings, click on Chats.
5) Turn off Media Visibility.
If you want to set for selected chat then follow these steps
1) First of all open WhatsApp.
2) After this, click on any chat for which you want to do this setting.
3) Now go to the three dot menu appearing on the right side.
4) Here you will get the option of View Contact, click on it.
5) After this you will see the option of Media Visibility, click on it.
6) After clicking, three options will appear in front of you – Default (Yes), Yes and No.
After changing the settings mentioned above, WhatsApp will not automatically download media files.

For iPhone users
1) First of all open WhatsApp.
2) Click on the Settings option appearing on the bottom right side.
3) Then go to Chats.
4) After clicking on chats, you will get the option of Save to camera roll, turn it off.