# How NotchStar finds duplicate files > Duplicates compares file contents, not names, across six folders. It skips files under 1 MB and hard links, and keeps the oldest copy of each set. Canonical: https://www.notchstar.com/help/find-duplicate-files-notchstar/ Last updated: 2026-11-04 Published 2026-11-04. To find duplicate files, open the Disk tab, pick **Duplicates** and press **Scan for duplicates**. NotchStar compares the contents of your files, not their names, and lists each set of identical copies. The oldest copy of each set is the one it keeps. ## Where and what it looks at - Folders: Downloads, Documents, Desktop, Pictures, Movies and Music inside your home folder. - Files of 1 MB or more. Smaller files are skipped. - Hidden files and the insides of app and other packages are skipped. - Symbolic links are skipped, and so are hard links. A hard link is the same file under two names, and removing one frees nothing. ## How it decides two files match 1. Group files by size. Different sizes cannot be identical. 2. For groups with the same size, hash the first and last 64 KB of each file. This is cheap and drops most false candidates. 3. For files that still match, compute a full SHA 256 of the whole content. Only files with the same full hash are called duplicates. Sets are sorted by how much space you could get back, and the sum is shown on the button. ## Removing copies Tick sets, then press the button that reads Move (size) of copies to Trash. The oldest file in each set stays, the rest go to the Trash. Check the keeper's location first. The oldest copy might sit in a folder you would rather not keep it in. ## Limits It does not look outside those six folders and it is not a general backup check. A large scan can take a while, see [why a Disk scan is slow](https://www.notchstar.com/help/why-notchstar-disk-scan-is-slow/). The [Disk feature page](https://www.notchstar.com/features/disk/) lists the other sections, and [the Trash step](https://www.notchstar.com/help/notchstar-disk-trash-not-permanent-delete/) explains how to undo a move. ## Quick answers. ### Does it match files with the same name? No. Names are ignored. Two files are duplicates only if their contents are identical. ### Which copy does it keep? The oldest, by modification date. The others are offered for the Trash. ## Keep reading. - [Disk space, duplicates, apps and cleanup](https://www.notchstar.com/features/disk/): See free space, find big folders, duplicates and app leftovers, compress media and clean caches from your Mac notch. Everything goes to the Trash. - [How the NotchStar Disk Trash step works](https://www.notchstar.com/help/notchstar-disk-trash-not-permanent-delete/): Disk moves items to the Trash and never deletes for good. Space only comes back when you empty the Trash yourself in Finder. - [Why a NotchStar Disk scan can be slow](https://www.notchstar.com/help/why-notchstar-disk-scan-is-slow/): Scans read real files: sizing folders, hashing duplicates and recompressing media all take time on big libraries. Here is what each one does. - [How to find what is filling your Mac, and free space safely](https://www.notchstar.com/blog/free-up-space-on-your-mac-without-a-cleaner/): Find what fills your Mac with Finder and Terminal, learn which folders are safe to clear, and what to leave alone. Commands tested, with a 20 minute routine. ## More in Disk and storage. - [What the NotchStar Disk scan finds](https://www.notchstar.com/help/what-notchstar-disk-scan-finds/): The Overview scan finds app caches, logs, Xcode build data and downloads untouched for 90 days. It lists them and removes nothing until you choose. - [Is NotchStar Disk cleanup safe?](https://www.notchstar.com/help/is-notchstar-disk-cleanup-safe/): Disk only moves things to the Trash, only inside your home folder and app bundles in /Applications. It refuses the home folder itself and system paths. - [How the NotchStar Disk Trash step works](https://www.notchstar.com/help/notchstar-disk-trash-not-permanent-delete/): Disk moves items to the Trash and never deletes for good. Space only comes back when you empty the Trash yourself in Finder. - [How to remove an app and its leftovers in NotchStar](https://www.notchstar.com/help/remove-app-leftovers-notchstar/): The Apps section lists apps with the caches, preferences and logs they leave in Library. Remove sends the app and those files to the Trash. - [How to compress large videos with NotchStar](https://www.notchstar.com/help/compress-large-videos-notchstar/): Compress finds photos over 2 MB and videos over 50 MB, recompresses them, and keeps the result only if it is under 90 percent of the original size. - [Why a NotchStar Disk scan can be slow](https://www.notchstar.com/help/why-notchstar-disk-scan-is-slow/): Scans read real files: sizing folders, hashing duplicates and recompressing media all take time on big libraries. Here is what each one does.