Duplicate File Finder
Add a batch of files and find the ones with byte-for-byte identical contents, whatever their names. Files are compared by size and SHA-256 hash in your browser and are never uploaded.
Drop files here to check for duplicates
Add up to 100 files at a time; add more batches to compare them all
Max 100 files, up to 50.0 MB each
About the Duplicate File Finder
Add a batch of files, press Find Duplicates, and the tool groups the files whose contents are exactly the same. File names do not matter: holiday.jpg and IMG_2041 (1).jpg are reported as duplicates if every byte matches, while two different files that share a name are not.
The check works in two stages. Files of different sizes cannot be identical, so first the tool groups files by size. Only files that share a size are then read and fingerprinted with SHA-256, using the browser's Web Crypto API (crypto.subtle.digest). Files with the same SHA-256 hash are listed together; the chance of two different files sharing a SHA-256 hash is so small that it is ignored in practice. Each group shows the file names, the size of each copy and the full hash.
A typical case: you have copied photos from a phone several times and want to know which copies are repeats before clearing space. Drop the files (or a folder, in browsers that support folder drag-and-drop) and the summary shows how many files there are, how many have unique contents, how many are extra copies and how much space those copies use.
The tool only reports. It cannot delete or move anything on your computer, because web pages are not allowed to; you keep one file from each group and delete the rest in your file manager. It also finds only exact copies: a resized, re-saved or edited photo has different bytes and will not match. To look inside a file before deleting it, open it in the File Viewer.
How to use the Duplicate File Finder
- 1
Add files
Drop files on the drop area or click Browse Files. You can add up to 100 files at a time and keep adding batches; the same file added twice is ignored.
- 2
Review the list
The Files list shows every file with its size. Use the bin icon to remove one, or Clear All to start over.
- 3
Find duplicates
Press Find Duplicates. The button shows progress while files with matching sizes are hashed.
- 4
Act on the results
Read the summary and the Duplicate Groups, then delete the extra copies yourself in your file manager.
What it can do
Content-based matching
Files are compared by SHA-256 hash of their bytes, not by name or date.
Size pre-check
Only files that share a size with another file are hashed, which saves time on mixed batches.
Clear summary
Total files, unique contents, extra copies and the space those copies take up.
Folder paths when available
Files dropped as part of a folder are listed with their folder path, so you can tell copies apart.
Local processing
Files are read and hashed inside your browser; nothing is uploaded.
Limitations
- Each file can be at most 50 MB, and a single drop or selection can hold at most 100 files; larger selections are rejected, so add them in batches.
- Only identical files are found; it does not detect similar photos, resized images or re-encoded music.
- It cannot delete, move or rename files. Browsers do not allow web pages to change files on your disk.
- Every file that needs hashing is read fully into memory one at a time, so very large batches can be slow.
- Empty (0-byte) files all count as duplicates of each other.
Privacy
Files are read and hashed in your browser with the Web Crypto API; neither the files nor their hashes are sent to FlexyPdf's servers.
Frequently asked questions
Does it compare file names?
No. Only the contents matter. Renamed copies are found, and different files that happen to share a name are not reported as duplicates.
How reliable is a SHA-256 match?
Two files with the same SHA-256 hash can be treated as identical. No two different inputs with the same SHA-256 hash have ever been found, which is why it is widely used to verify downloads and backups.
Can it find similar photos, not just exact copies?
No. A photo that was resized, cropped, compressed again or edited has different bytes and a different hash, so it will not be grouped with the original.
Can it delete the duplicates for me?
No. Web pages cannot delete files on your computer. Use the groups as a checklist and remove the extra copies in File Explorer, Finder or your phone's file manager.
Are my files uploaded to check them?
No. The hashes are calculated on your device, and nothing is sent to FlexyPdf. You can confirm this in your browser's network tab.
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