Duplicate File Finder

What this tool does

Duplicate File Finder computes a SHA-256 hash of every file in a selected batch, entirely in your browser, and groups files with identical hashes, revealing true content duplicates even when they have completely different filenames.

Two files with completely different names can still be byte-for-byte identical in content, a photo downloaded twice under different names, or a document copy renamed and forgotten about, duplicates that a simple filename comparison would never catch.

This tool computes a SHA-256 hash, a unique fingerprint, for every file in a selected batch entirely in your browser, then groups files whose hashes match exactly, revealing genuine content duplicates regardless of what they’re named.

How to use Duplicate File Finder

1. Select the batch of files you want to check.
2. Wait while each file is hashed (progress shown live).
3. Review any duplicate groups found, each listing the identical files within it.
4. Remove or consolidate the extra copies in each duplicate group as needed.

Tips for better results

• A SHA-256 match means the files are genuinely, exactly identical byte for byte, not just similar; even a single-byte difference produces a completely different hash.
• Files with different names but identical content (like "photo.jpg" and "photo (1).jpg" from an accidental double-download) are exactly the kind of duplicate this catches that a filename-only comparison would miss.
• Two files that look visually similar but were saved at different quality or resolution (like a resized copy of the same photo) are NOT detected as duplicates, since their actual byte content differs even though they depict the same thing.
• Hashing happens entirely in your browser, which is more private than uploading files to an online duplicate-checking service, but also means very large batches take real local CPU time.

Common use cases

• Finding accidental duplicate downloads or copies among a batch of files before organising them.
• Checking whether two differently-named files actually contain identical content.
• Cleaning up a messy downloads folder by identifying true duplicates to remove.
• Verifying that a backup copy of a file is byte-for-byte identical to the original.

Common mistakes to avoid

• Expecting visually similar but differently-processed files (a resized or re-compressed copy of the same image) to be flagged as duplicates; only byte-for-byte identical content produces a matching hash.
• Assuming two files with the same name are automatically duplicates; this tool checks actual content via hashing, not filenames, two differently-named identical files are correctly flagged while two same-named but different files are correctly not.
• Hashing an extremely large batch of big files and expecting instant results; hashing time scales with total data size and runs entirely on your own device.