Starting with iOS 16, the Photos app can detect duplicate photos and videos in your photo library and place them in the Duplicates album under the Utilities section.
For the Duplicates album to appear, iPhone has to first complete the following steps:
- Index your photo library.
- Find duplicates.
The detection process requires iPhone to be locked and connected to a power source. Depending on what tasks are running in the background and the size of your photo library, the process could happen quickly or take up to a few days to complete.