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How to Find and Delete Duplicate Files on Windows

2026 · 5 min read

Duplicate files build up quietly: a photo backed up twice from two different apps, a document copied "just in case" and never removed, a downloads folder with three copies of the same installer. None of it looks like much file by file, but it adds up.

How duplicates actually accumulate

• Photo and video backups - syncing the same camera roll through more than one app or cloud service is the single biggest source for most people.
• Downloads - re-downloading a file because the original couldn't be found, without deleting the old one.
• Project folders - copying a whole folder to "make a backup" before an edit, then keeping both indefinitely.
• Email attachments - saved once from the email client and again manually, in two different folders.

Why file name and size aren't enough

Two files can have the same name and be completely different, and two files with completely different names can be byte-for-byte identical (a renamed copy, for instance). Reliable duplicate detection has to compare actual content, not just the file's name or reported size, otherwise you'll get false matches and miss real ones.

How real duplicate detection works

The efficient approach is two steps: first group files by size, since two files with different sizes obviously can't be identical. Then, only for files that share a size with at least one other file, compute a content hash (a fingerprint of the actual bytes) and compare those. This avoids the expensive part, hashing, for the vast majority of files that have no size match at all.

Safety before deleting

• Delete to the Recycle Bin, not permanently, so a mistake is recoverable.
• Check the full path of each copy before removing one, sometimes "duplicates" are intentionally kept in different locations for different purposes (a working copy and an archive copy).
• Start with your largest duplicate groups first, that's where the actual space savings are.

What it doesn't do (on purpose)

PurgeCore shows you duplicates, it doesn't delete anything automatically. That choice is intentional: automatic deletion of "duplicate" files is exactly the kind of feature that goes wrong for someone, somewhere, and costs them a file they actually needed.