Duplicate File Finder
Find exact duplicate files by content hash, regardless of their filenames.
What is Duplicate Finder?
A content-based duplicate finder. Copies that were renamed, moved or received twice are all caught, because the comparison uses the file's bytes rather than its name.
How it works
Each file is read and hashed with SHA-256 — the same digest used for release verification. Files sharing a digest are grouped, the first in each group is marked as the one to keep, and the redundant copies are packed into a .zip alongside a CSV report.
- Add your files. Drop files (or a whole folder) onto the drop zone. Browsers hand the contents straight to the page, so nothing is uploaded.
- Choose the options. Pick the format, compression, naming rule or split size. Any change re-computes the preview immediately.
- Download the result. Run the tool and grab the archive, the extracted files or the report. Multi-file results come back as a single .zip.
Examples
A 240 MB photo folder → a 52 MB .zip
JPEGs are already compressed, so the archive only saves 10–15% — but adding the folder structure and a manifest makes the upload verifiable.
A download cut off at 1.4 GB
The File Splitter cuts it into 500 MB chunks that fit the host's limit, and the File Joiner reassembles them, refusing any set with a missing part.
A release bundle with checksums
The Manifest Generator writes sha256sum-style lines next to the files, so the recipient can prove the download arrived intact.
Common mistakes
Expecting ZIP to shrink photos, video or audio
Those formats are already compressed; deflate typically saves single digits on them. ZIP is at its best on text, JSON, CSV, logs and source code.
Treating ZipCrypto as real encryption
Traditional ZIP encryption is legacy and breakable. It stops casual snooping only — for secrets, encrypt the contents with AES-256 first.
Renaming extensions to convert a file
Changing .png to .jpg does not change the bytes inside. Some programs will refuse the file, or display garbage. Use a real converter when the format must change.
Splitting without keeping the suffixes
The parts carry .001, .002 … suffixes on purpose: the joiner orders them by number and fails loudly when one is missing, instead of producing a corrupt file.
Frequently asked questions
Can two different files share a SHA-256 hash?
There is no known way to produce a collision, and finding one by accident is astronomically unlikely. Identical hashes mean identical bytes for every practical purpose.
Does it delete anything?
Never. It reports groups and hands you the redundant copies in an archive — you decide what to remove, and you still have the originals.
Why is a folder of 20,000 files slow?
Every byte of every file must be read and hashed; that is the point of the tool. Hashing is single-threaded in this page, so budget roughly a second per 100 MB.