Question 1

What does the Duplicate File Finder do?

Accepted Answer

It scans the files you drop, groups them by size, and for any files sharing a size, computes a SHA-256 hash to confirm whether they are byte-for-byte identical. You get a list of duplicate groups with file paths, sizes, and how much space you'd save by removing the extras.

Question 2

Why does it use a partial hash first?

Accepted Answer

Computing SHA-256 on large files is slow. We hash only the first 4KB of each file as a quick filter — only if two files share both their size AND their first-4KB hash do we compute the full SHA-256 to confirm. This makes scanning 100s of files dramatically faster.

Question 3

What hash algorithm is used?

Accepted Answer

SHA-256 via the browser's built-in WebCrypto API. This is the same primitive used for file integrity verification and TLS certificates.

Question 4

Can I delete the duplicates?

Accepted Answer

Yes, on Chromium browsers with the File System Access API you can open a folder and delete the duplicate files in-place. On other browsers, you can export the duplicate list (CSV or JSON) and delete manually.

Question 5

What extra features does this tool have?

Accepted Answer

10 extras: (1) Drag-drop multiple files at once. (2) Progress bar during scan. (3) Partial-hash (first 4KB) quick filter. (4) Full-hash confirmation only when needed. (5) Live stats (total files, duplicates found, space saved). (6) Filter by size threshold (ignore files < N KB). (7) Sort by size / name / date. (8) Export as CSV or JSON. (9) History (localStorage — last 10 scans). (10) Shareable URL with scan settings.

Question 6

Are my files uploaded anywhere?

Accepted Answer

No. All hashing runs in your browser using WebCrypto. Your files never leave your device.

Question 7

What's the maximum number of files?

Accepted Answer

There's no hard limit, but scanning 1000+ large files may take a while and use significant memory. We process files in chunks and show progress.

Duplicate File Finder

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