File Hash Checksum Calculator
Calculate a file's hash to verify its integrity, with the common algorithms and their uses explained.
A fingerprint for a file
A hash is a short string of characters computed from a file's contents that acts as a unique fingerprint — the same file always produces the same hash, and any change, even a single byte, produces a completely different one. This calculates a file's hash in your browser, so the file never leaves your device.
What hashes are used for
Hashing has a few important uses, and different algorithms suit different purposes:
| Algorithm | Typical use | Note |
|---|---|---|
| MD5 | Quick integrity checks | Fast but not secure against tampering |
| SHA-1 | Legacy integrity checks | Now considered weak for security |
| SHA-256 | Integrity and security | The modern standard |
The most common everyday use is verifying a download: a site publishes the expected hash of a file, and after downloading you compute the file's hash and compare — if they match, the file arrived complete and unaltered.
Integrity, and a note on security
The power of a hash for integrity checking is that it detects any change at all — a corrupted download, a truncated transfer, or deliberate tampering all change the hash completely, so a matching hash gives strong confidence the file is exactly what it should be. For security purposes, like verifying a file has not been maliciously altered, the algorithm matters: older ones like MD5 and SHA-1 can be deliberately fooled and are no longer trusted for security, while SHA-256 remains the standard. A useful property throughout is that a hash cannot be reversed to reveal the file, and it is a fixed short length regardless of the file's size. Because this computes the hash locally in your browser, you can verify sensitive files without uploading them anywhere, which is exactly what integrity checking should allow.
File Hash Checksum Calculator FAQ
What is a file hash?
A short fingerprint computed from a file's contents — the same file always gives the same hash, and any change produces a completely different one.
How do I verify a download with a hash?
Compute the downloaded file's hash and compare it to the expected hash the site publishes. If they match, the file arrived complete and unaltered.
Which hash algorithm should I use?
SHA-256 is the modern standard for both integrity and security. MD5 and SHA-1 are faster but no longer trusted against deliberate tampering.
Can a hash be reversed to get the file back?
No — a hash cannot be reversed to reveal the file, and it is a fixed short length regardless of the file's size.
Is my file uploaded?
No. The hash is computed in your browser, so the file never leaves your device.