What is a hash?

A hash function turns any input into a fixed-length fingerprint. Even a one-character change produces a completely different hash — which makes hashes ideal for verifying that data has not been tampered with.

Which algorithm should I use?

• SHA-256 / SHA-512 — the modern standard for integrity checks and signatures.
• MD5 / SHA-1 — fine for non-security checksums, but cryptographically broken; never use for passwords.

Frequently asked questions

Can a hash be reversed? No — hashes are one-way. (Attackers guess common inputs instead.)
How do I verify a download? Hash the file’s contents and compare with the publisher’s published checksum.
Is my text uploaded? No — hashing runs entirely in your browser.