A hash is a fixed-length fingerprint of some data. Feed in the same input and you always get the same hash; change a single character and the hash changes completely. That property makes hashes perfect for checking whether two things are identical — like a download and its published checksum.
What a hash is for
- Verifying downloads — compare the hash of a file you downloaded to the one the publisher lists; if they match, the file is intact.
- Detecting change — store a hash now and re-check later to see whether a file was modified.
- Storing passwords — systems store a salted hash, not the password itself, so a breach does not immediately reveal it.
How to generate one
- Open the hash generator.
- Paste your text and pick the algorithm — prefer SHA-256 over MD5 or SHA-1.
- Copy the hash. It is computed in your browser, so your input stays private.
A hash is one-way
You cannot 'decrypt' a hash back into the original data — the process deliberately throws information away. The only way to find what produced a hash is to try inputs until one matches, which is why weak, unsalted hashes of common passwords can be cracked and strong, salted ones resist it.
MD5 and SHA-1 are fine for a quick 'did this file change?' check but are considered broken for security. Use SHA-256 whenever the answer actually needs to be trustworthy.