File Hash Checker
SHA-256 hash generation — verify file integrity without uploading anything.
Drop any file here or click to select
Supports any file type — computed entirely in your browser
Prove a delivered file is the file you sent
A hash is a short fingerprint computed from a file's contents. Change a single byte and the fingerprint changes completely, which makes it a cheap and conclusive way to answer two questions freelancers hit regularly: did this download arrive intact, and is the file the client is complaining about actually the one I delivered. Computing it locally is the only sensible approach — uploading a file in order to learn its fingerprint defeats the purpose of checking it.
How This Local-First Tool Works
- Record the SHA-256 of a final deliverable when you hand it over, and put it in the delivery email. If a dispute later turns on whether the file was modified after delivery, you have something considerably better than recollection.
- Hashes verify integrity, not authorship. A matching hash proves the file is unchanged; it does not prove who produced it. Establishing that requires a signature, which is a different mechanism entirely.
- Any difference produces a completely different hash — there is no such thing as a nearly-matching one. If two hashes differ at all, the files differ, even when they look identical on screen.
- SHA-256 is the sensible default. MD5 and SHA-1 still appear beside downloads but both have practical collision attacks, so a match no longer proves a file is the intended one; treat them as corruption checks only.
Frequently Asked Questions
- What is a file hash actually for?
- Two things in practice: confirming a download was not corrupted in transit, and proving a file has not been altered since a known point in time. Publishers list a hash beside a download precisely so you can check that what arrived matches what they published.
- Which algorithm should I use?
- SHA-256 unless something specifically requires otherwise. MD5 and SHA-1 can be deliberately collided, meaning two different files can be made to share a hash, so a match no longer proves much beyond the absence of accidental corruption.
- Does hashing change or protect my file?
- Neither. The file is read and a fingerprint computed; nothing is written and nothing is encrypted. A hash tells you whether a file changed — it cannot prevent anyone from changing it.
- Is my file uploaded to compute the hash?
- No. It is read and hashed by your browser using the Web Crypto API. Uploading a confidential file in order to verify its integrity would be self-defeating, and plenty of online hash tools do exactly that.
- How do I use this in a client dispute?
- Hash the deliverable at handover and state the value in the delivery email, which timestamps it. If the client later produces a file they say you sent, hashing their copy either matches your record or does not. It will not settle a disagreement about quality, but it settles one about whether the file was altered.
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