SHA-3 Hash Generator

How to use the sha-3 hash generator

1. Pick a variant, and an output length if you chose SHAKE.
2. Type or paste text, or choose a file.
3. Copy the hash, or paste a published checksum to compare.

About this tool

SHA-3 is not an upgrade to SHA-256, and choosing it for that reason is a misunderstanding worth correcting. It was standardised as insurance: it is built on a completely different construction — a sponge, rather than the Merkle–Damgård design behind MD5, SHA-1 and SHA-2 — so a break in that family would not carry over. SHA-2 remains unbroken and is the sensible default; SHA-3 is the right choice when a specification calls for it.

Browsers do not implement SHA-3. The Web Crypto API offers SHA-1 and the SHA-2 family and nothing else, so this is computed by an implementation on the page rather than by the browser. That implementation is checked against the published NIST test vectors for every variant, including inputs at exactly the block boundary and either side of it, which is where padding mistakes hide — a wrong padding byte produces a hash that looks perfectly plausible and matches nothing.

SHAKE128 and SHAKE256 are included because they are the interesting part of the family. They are extendable-output functions: they produce as many bytes as you ask for rather than a fixed digest, which makes them usable as key derivation and stream generation as well as hashing. The number in the name is the security level, not the output length.

Files are hashed in the same tab as text, so a checksum can be verified against a published one without sending the file anywhere — which matters, since the files people most want to verify are the ones they have just downloaded from somewhere they are not sure about.

Common uses

• Producing a SHA3-256 digest a specification asks for.
• Verifying a download against a published SHA-3 checksum.
• Generating arbitrary-length output with SHAKE.

Frequently asked questions

Is SHA-3 more secure than SHA-256?

Not in practice — SHA-256 is unbroken. SHA-3 exists as insurance, built on a different construction so a break in the SHA-2 family would not affect it.

Why is SHA-3 not in the browser already?

The Web Crypto API only offers SHA-1 and SHA-2. SHA-3 has to come from an implementation on the page, which is what this is — checked against the NIST vectors.

What is SHAKE?

An extendable-output function: it produces as many bytes as you ask for rather than a fixed digest. The number in the name is its security level, not its output size.