Same bytes, same hash
An unchanged file produces the same checksum every time under the same algorithm.
Trust the file.
Check the fingerprint.
Calculate a standard cryptographic checksum and compare it with the publisher’s value—without handing the file to another server.
Files never leave your device. Your browser reads each file locally and computes its checksum with the built-in Web Crypto API.
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Drop the files you want to verify
Files are processed one at a time to be kinder to memory. Very large files still need enough free browser memory to be read.
The useful details01 02 03
A deterministic answer beats a confident guess.
One changed byte matters
A modification should produce a substantially different cryptographic fingerprint.
The source still matters
Compare against a checksum delivered through a publisher channel you already trust.
Checksum questions.
Which algorithm should I choose?
Use the same algorithm named by the publisher. SHA-256 is the most common modern file checksum. SHA-384 and SHA-512 produce longer values.
Does a matching checksum prove a file is safe?
It proves that your file matches the bytes represented by the expected checksum. It does not prove the original publisher or software is trustworthy, so the source of the expected value still matters.
Why is MD5 not included?
MD5 is still encountered as an accidental-corruption checksum, but it is not collision resistant enough for modern security verification. This tool keeps the main path on the SHA-2 family.
Why can a very large file take time?
The browser must read the file and perform the digest locally. This version uses the browser’s standard cryptographic API, which may hold the file data in memory while calculating.