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Glossary Data & Encoding

Checksum

A checksum is a small value calculated from a block of data and used to detect accidental errors when the data is stored or sent.

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In more detail

The receiver recomputes the checksum and compares it with the one sent; a mismatch means the data changed. Simple ones such as CRC-32 catch random corruption cheaply but are not secure against deliberate tampering, for which a cryptographic Hash such as SHA-256 is used. Download pages often list a checksum so you can verify the file.

Example

The CRC-32 of hello is 3610a686.

Try these tools

File Checksum Calculator

Calculate MD5, SHA-1, SHA-256, SHA-384, SHA-512 and CRC-32 checksums of one or many files and compare them with a published value.

Hash Generator

Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from any text, computed locally with the Web Crypto API.

See also

  • Glossary Hash
    A hash is the fixed-length fingerprint a hash function computes from any input; the same input always gives the same hash.
  • Guide How Hashing Works
    What a hash function does, the avalanche effect shown with real SHA-256 output, which algorithms are still safe, HMAC.
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