A cryptographic hash function maps data of any size to a fixed-length value. SHA-256 produces a 256-bit digest, commonly displayed as 64 hexadecimal characters. A small change to the input normally produces a very different digest.
Comparing a Download
If a publisher provides a SHA-256 value through a trusted channel, you can calculate the downloaded file's digest and compare the two values. A match is evidence that the file contents match the value you received. It does not prove that the publisher or file is safe if the source itself is compromised.
Use the File Checksum Verifier to calculate a digest in the browser and compare it with an expected value. Select the correct algorithm: SHA-256 and SHA-512 produce different outputs, so their values are not interchangeable.
Hashes Are Not Password Encryption
A hash is not designed to be decrypted back into its input. However, a plain hash is not appropriate for storing passwords: password storage systems need dedicated, salted, slow password-hashing methods. A general-purpose hash generator is useful for checksums and developer tasks, not password protection.
For important downloads, obtain the expected checksum from the publisher's official source, use the algorithm they specify, and compare the complete value carefully.