A fingerprint for your data
A hash is a string of characters that works like a digital fingerprint for a file, a word, or a transaction. The same input always produces the same result.
What is a hash?
A digital fingerprint that turns any input into a fixed-length string. Type something and watch it change.
Its SHA-256 fingerprint
Change one letter and see what happens.
Small change, big difference
Change just one letter and the hash changes completely. This makes hashes useful for checking whether information has been altered.
The role of hashes in Bitcoin
Bitcoin uses hashes to link blocks and protect its history. Each block includes the fingerprint of the previous one: changing a piece would make the change evident.