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File Fingerprint

Build an identity bundle for a file: size, declared-vs-detected MIME, hashes (SHA-1 / SHA-256 / SHA-512), optional HMAC, and a hex head preview. "Is this file exactly what I think it is?" in one drop.

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About File Fingerprint

File Fingerprint builds a complete identity bundle for any file you drop in: its size, the declared-versus-detected MIME type, SHA-1 / SHA-256 / SHA-512 hashes, an optional HMAC, and a hex preview of the opening bytes. Reach for it when you need to answer one question with confidence: "is this file exactly what I think it is?" Everything is computed in your browser, so even sensitive files never leave your device.

Category
inspect
Input
Accepts: */*.
Output
Outputs: application/json.
Cost
Free, runs in your browser
Memory
low
Privacy: File Fingerprint runs entirely on your device. Files you provide never leave your browser — no uploads, no server, no tracking. The page works offline once loaded.

Common uses

  • Confirm a downloaded installer matches the SHA-256 the vendor published before you run it
  • Catch a file whose extension says .png but whose detected MIME is actually a PDF or executable
  • Generate an HMAC over a payload using a shared secret to prove it came from a trusted source
  • Record a SHA-512 of a contract or evidence file so you can prove it hasn't changed later
  • Eyeball the hex head of an unknown blob to spot magic bytes like %PDF, PK, or ‰PNG
  • Produce a one-drop integrity report for a build artifact before attaching it to a release

Frequently asked questions

What file types can I fingerprint?

Any file at all. It accepts every MIME type, since hashing and MIME detection work on raw bytes regardless of format.

Does my file get uploaded anywhere?

No. Hashing, MIME sniffing, and HMAC all run client-side in your browser, so the file's bytes never leave your machine.

What's the difference between declared and detected MIME?

Declared MIME is what the browser infers from the file's name and extension; detected MIME is read from the actual leading bytes. A mismatch is a strong sign the file isn't what its name claims.

Which hash algorithms are included?

SHA-1, SHA-256, and SHA-512 are all computed in a single pass, plus an optional keyed HMAC if you supply a secret.

Is there a file-size limit?

There's no hard cap, but very large files are read entirely into memory in the browser, so multi-gigabyte files may be slow or constrained by your available RAM.

Keywords

  • fingerprint
  • identity
  • hash
  • sha256
  • hmac
  • mime
  • verify
  • integrity

Try next

Hash
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When you only need a plain SHA checksum of a file without the full identity bundle.
Strip EXIF Metadata
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If the fingerprint reveals an image, remove its hidden EXIF/GPS metadata before sharing.
Base64
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Encode the same file to Base64 text when you need to embed or transmit it inline.
Color Palette
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Extract dominant colors from an image as hex codes.
Image Diff
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Pixel-level diff between two images of the same dimensions.
Image Info
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Extract dimensions, format, and metadata from an image.
PDF Info
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Extract page count and metadata from a PDF.
Hash
inspect

Compute SHA-256, SHA-1, or SHA-512 hashes of files.
JSON Formatter
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Parse and pretty-print JSON with configurable indentation.
Extract PDF Tables
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Extract tabular data from a PDF as JSON or CSV. Works well for simple tables with aligned columns and no merged cells. Complex tables, rotated text, and scanned PDFs (images) will not extract cleanly.
Topic Keywords
text

Pull the topic-bearing nouns and noun phrases out of any text. Answers "what is this about" — not "what words appear most" (try Text Frequency for that). Runs entirely in your browser.