Windows 11 has no built-in duplicate-photo finder, and the two methods usually suggested — sort by name, sort by size — both fail on photos specifically.
Why they fail
Camera and phone filenames repeat. IMG_4821.jpg from a 2022 import and IMG_4821.jpg from a 2024 import are two different photos that happen to share a name. Sorting by name groups them together and invites you to delete the wrong one.
Size is worse. Two photos can both be exactly 4,096 KB and be completely unrelated images. Size narrows the candidate list; it never confirms anything.
The check that actually answers the question
Read the bytes and hash them. If two files produce the same SHA-256 digest they are identical — not similar, identical. A resized or re-encoded copy is a different file with a different hash, so this method will not propose deleting a photo you deliberately edited.
Doing it efficiently is a three-pass job, cheapest first:
- Group by exact byte size. This alone eliminates almost everything.
- Hash the first 4 KB of whatever survives.
- Only for the files that still match, read the whole file and hash it.
On a few hundred thousand photos this finishes in minutes instead of hours, and the output is a set of groups where every file in a group is byte-for-byte the same.
Before you delete anything
- Keep the copy in the folder you would look in first — Pictures\2024\ rather than Downloads.
- Check whether something references the file: a Photos album, a Lightroom catalog, an attachment embedded in a project. Deleting it breaks that reference even though an identical copy still exists elsewhere.
- Send files to the Recycle Bin rather than deleting permanently, then empty it a week later. That week is your entire safety margin.
- Watch for hard links. Two names pointing at the same data look like duplicates but free zero bytes when removed. A tool that counts them is overstating how much space you will get back.
On the Microsoft PC Manager suggestion above: Storage > Duplicate files does the size and hash comparison for you and is safe to try. Its limitation is coverage — it only looks where it scans. If your duplicates are on a second drive or an old backup folder, point a duplicate finder at those folders specifically instead of scanning C: and hoping it reaches them.