How to delete duplicate photos on iPhone
Use the Duplicates album in Photos for exact copies and Bursts for burst shots. For near-identical retakes, group similar photos and keep the sharpest one.
What does Duplicate Photos find?
Two kinds of groups. Byte-identical copies are the same file stored twice, for example an image that arrived in two chats. They always come down to a single copy. Near-identical shots are different files of the same moment: a burst, three attempts at the same smile, the same view taken seconds apart.
How does DustFox know two photos are the same?
Each photo is reduced to a small grayscale image and turned into a 256-bit fingerprint built from its DCT (discrete cosine transform), the same mathematics JPEG uses to describe the structure of an image. Photos with close fingerprints land in the same group. Because the fingerprint describes structure rather than bytes, it still matches after resizing or recompression.
The whole analysis runs on small buffers of 64 to 160 pixels. Full-resolution data is never opened for it, which keeps memory use and time steady even in large libraries.
Which photo does it keep?
A jury of measures decides: sharpness, exposure, resolution and file size. Each measure compares the shots in pairs. If the difference is smaller than that measure’s own noise, it calls a tie and casts no vote. Sharpness is measured on the sharpest region of the frame rather than the average, so a portrait with a deliberately soft background is not punished for it.
Open any group to see how the vote went, measure by measure, and choose a different keeper if you disagree.
What is never suggested for deletion?
Favorites, and shots iOS won’t let you delete because they were synced from a computer or came from a shared album. Shots you chose to keep elsewhere in DustFox stay out as well.
Does it work with iCloud Photos?
It compares shots whose original is on the device, because the analysis has to read the shot itself. Those are also the only duplicates that free device space when deleted.
