Duplicate photo remover for iPhone

Two different things, one misleading word

An exact duplicate is a real copy of a picture you already have: the same image saved twice, a photo you saved from a chat that was already in your library, a shot copied out of and back into the camera roll. Deleting one of them costs you nothing at all.

A similar shot is a different photograph. Three frames of a burst, two attempts at the same group picture, the same view a second apart. They look alike but they are not copies, and the one you keep is a decision, not a formality.

An app that folds both into a single "duplicates" number has an easier headline. It also has a number you cannot check, and a delete button that can take a photograph you would have kept.

How Nixly separates them

Exact duplicates

Nixly renders each still image down to a tiny greyscale thumbnail and computes a 64 bit difference hash from it, comparing the brightness of neighbouring pixels. That fingerprint is combined with the image's own pixel dimensions, and photos are grouped only when both match. Two pictures reach the same group when they are the same image at the same size.

The honest limit: this identifies the image, not the file. If you have the same picture twice at identical dimensions but saved at different compression settings, Nixly groups them as duplicates. In practice that is usually what you want, because one of the two is a re-saved copy. It is still not the same claim as byte for byte identity, and we would rather describe it accurately than borrow a stronger word.

Similar shots

Similar photos are found with Apple's Vision framework, which produces a feature print for each image. Nixly compares those feature prints and groups photos whose distance falls under a fixed threshold. Crucially it only compares photos taken within 60 seconds of each other. Bursts and repeated attempts happen in the same moment, so a short time window catches them, and it means your holiday beach photo is never grouped with a different beach from another year.

The honest limit: a photo with no creation date cannot be placed in a time cluster, so it is not compared for similarity. That is rare, and it mostly affects images imported through unusual routes.

The rule that keeps the totals checkable

The two categories never overlap. Anything Nixly has already grouped as a duplicate is removed from the pool before similar shots are grouped, and removed again before the screenshot list is built. One photo appears in exactly one category, so the four category totals add up to the headline figure without anything being counted twice.

Every one of those totals is the sum of measured file sizes. Nixly requests the actual image data for each photo it is going to show you and adds up the real bytes. Nothing is inferred from resolution.

Which copy gets kept

In every group Nixly picks a keeper and marks it BEST. The rule runs in a fixed order:

1. The highest resolution shot.
2. If two are equal, the larger file.
3. If those match too, the newest.

That keeper is excluded from the pre-selection, and it is excluded from the swipe deck entirely, so it is not possible to swipe away the best copy in a group by accident. You can still select it by hand if you want to, but nothing pre-selects it for you.

Do you need an app for this at all?

For exact duplicates, often not. iOS 16 and later ships a Duplicates album under Photos > Albums > Utilities that finds exact duplicates and merges them, keeping the highest quality version. It is free, first party, and you should run it first. There is a full comparison on the iPhone Duplicates album versus a cleaner app.

Where the built in album stops is bursts, screenshots as a category, videos by size, and per group size figures. On most camera rolls the bursts are the larger pile.