SHA-256 hash generator
See the SHA-256 hash of any text, the hash function behind Bitcoin, and watch how changing one character changes the whole hash. Free, no sign-up, worked out in your browser.
Text is hashed exactly as typed, including spaces and capitals, using UTF-8. Never paste a seed phrase, private key or password into any website, this one included.
What a hash is
A hash function turns any amount of data into a short, fixed-length fingerprint. SHA-256 always gives 256 bits, shown as 64 hexadecimal characters. The same input always gives the same hash, but you can't work backwards from a hash to the input, and changing a single character changes the hash completely.
How blockchains use it
Bitcoin uses SHA-256 to link each block to the one before it, so changing an old transaction would change every hash after it. Miners repeatedly hash block headers looking for a hash below a target, which is what proof of work means. Hashes also help build Bitcoin addresses and transaction IDs.
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