What a hash function does
A cryptographic hash turns any input — a word, a file, a gigabyte of data — into a fixed-length fingerprint. The same input always produces the same digest, a tiny change produces a completely different one, and you cannot work backwards from the digest to the input. That makes hashes the standard tool for verifying downloads, deduplicating data, indexing content, and building the integrity checks underneath signatures and blockchains.
Hex and Base64 are the same digest
A digest is just bytes: 16 bytes for MD5, 32 for SHA-256, 64 for SHA-512.
Hex shows each byte as two characters; Base64 packs three bytes into four
characters, so it is shorter. The Show Base64 button switches every row
between the two — the underlying digest is identical, only the encoding
changes. SHA-256 of the empty string, for instance, is the well-known
e3b0c442… in hex.
Which algorithm to use
MD5 and SHA-1 are both broken for collision resistance: researchers can deliberately construct two different inputs with the same digest. They are still perfectly fine as fast checksums — verifying a file downloaded intact, or keying a cache — but must never be used for digital signatures, certificates, or anything an attacker could exploit. Use SHA-256 or SHA-512 there. And for storing passwords, none of these is appropriate: a general-purpose hash is far too fast, which makes brute-forcing cheap. Password storage needs a deliberately slow function such as bcrypt, scrypt, or Argon2.
Computed locally
The SHA family here comes from your browser's built-in WebCrypto engine and MD5 from a small local implementation; either way the text you type is hashed in the page and never sent to a server. That matters when you are hashing anything sensitive — a secret, a token, a private document.
Related tools: the CRC calculator covers error-detection checksums (fast, but not tamper-proof), the Base64 converter handles encoding of arbitrary bytes, and the password entropy calculator shows why fast hashes like these make crack times so short.