Use iCloud Photos on iPhone
iCloud Photos automatically uploads the photos and videos you take and stores them in their original format at full resolution. You can access your photos and videos in iCloud Photos from any device where you’re signed in with your Apple ID.
To use iCloud Photos, you need a device that meets these minimum system requirements: iOS 8.1, iPadOS 13, OS X 10.10.3, or a PC with iCloud for Windows 7.
Turn on iCloud Photos
Go to Settings > [your name] > iCloud > Photos, then turn on iCloud Photos.
Save space on your iPhone
iCloud Photos keeps all your photos and videos in their original, high-resolution format. You can optimize storage to save space on your iPhone.
Go to Settings > [your name] > iCloud > Photos, then tap Optimize iPhone Storage.
View and share a full-resolution photo or video
Select a photo or video from your Library, then tap Edit.
The full-resolution photo or video downloads automatically.
Tap , then choose the device that you want to share it with.
Upgrade your iCloud storage to store more photos
If your uploaded photos and videos exceed your storage plan, you can upgrade your iCloud storage.
Go to Settings > [your name] > iCloud > Manage Storage > Change Storage Plan.
See the Apple Support article Set up and use iCloud Photos.