How to find duplicate files
- Choose a folder (subfolders are included), pick files, or drop them on the box. You can add more than once.
- Optional: turn on Also find similar images to catch resized or re-saved copies of the same photo.
- Press Find duplicates. Review each group with its previews, and download the CSV report to work through the list.
The tool is read-only. It shows you where the copies are, and you decide what to delete. For photos, keep the largest or oldest copy, and check that both paths are not the same file on two drives that you back up on purpose.
Questions
Are my files uploaded?
No. The files are read and compared by your browser, on your device. Nothing is sent to a server, and the folder you choose stays private.
How are duplicates found?
First the files are grouped by size, since files of different sizes cannot be identical. Files with the same size are then compared by their SHA-256 fingerprint. Two files with the same fingerprint are the same bytes, whatever their names are.
What does "similar images" do?
It shrinks every picture to a tiny grayscale version and compares the light and dark pattern. Copies that were resized, re-saved, or lightly edited come out nearly the same. Turn the slider down for stricter matches and up to catch more, with a higher chance of false matches.
Can it delete the duplicates for me?
No, on purpose. Browsers should not delete files from a tool that you just opened. Use the CSV report, then delete the extra copies in your file manager. Check the paths first, because the tool cannot know which copy you want to keep.
Is there a size limit?
There is no fixed limit. Files are read in small pieces, so large videos work. Checking thousands of big files takes time and your browser tab stays busy, so use the Stop button if needed.
Credits
Built on hash-wasm (MIT). OneTooling is not affiliated with that project.