You can easily check your phone to find out what is taking up storage space on the device. It could be files you have saved, photos you’ve taken etc.
How do I view storage usage?
Click the ‘Settings’ app.
Click ‘General’.
Click ‘iPhone Storage’.
A list of your apps, will be displayed showing how much storage space each app is using. They will be listed in descending order, the app using the most storage will be displayed at the top.