What is SHA3-256?
SHA3-256 is part of the SHA-3 family, standardized by NIST in 2015. Unlike SHA-1 and SHA-2, SHA-3 is built on the Keccak sponge construction, a fundamentally different internal design. SHA3-256 produces a 256-bit digest (64 hexadecimal characters) with security comparable to SHA-256, and it resists the length-extension attacks that affect SHA-2. It is a good choice when you want a modern, structurally different hash alongside or instead of SHA-2.
Modern & secure: SHA3-256 is a current NIST standard with a design completely different from SHA-2, and it runs entirely in your browser.
How SHA3-256 works
SHA-3 uses a sponge construction rather than the Merkle–Damgård design of SHA-1/SHA-2:
- Absorb — the padded message is split into blocks, and each block is XORed into a large internal state, which is then scrambled by the Keccak-f permutation.
- Permute — Keccak-f mixes the state through a series of step mappings (theta, rho, pi, chi, iota) repeated for many rounds.
- Squeeze — once all input is absorbed, 256 bits are read out of the state to form the digest.
This structure makes SHA-3 immune to the length-extension attacks that affect SHA-2.
How to use
- Type or paste your text into the input box.
- The SHA3-256 hash is calculated automatically as you type.
- Choose your output encoding (Hex or Base64) if needed.
- Click Copy to copy the digest to your clipboard.
Examples
| Input | SHA3-256 hash |
|---|---|
abc | 3a985da74fe225b2045c172d6bd390bd855f086e3e9d525b46bfe24511431532 |
hello | 3338be694f50c5f338814986cdf0686453a888b84f424d792af4b9202398f392 |
(empty string) | a7ffc6f8bf1ed76651c14756a061d662f580ff4de43b49fa82d80a4b80f8434a |
Options explained
- Output encoding — Show the digest as lowercase or uppercase Hex, or as Base64.
- Input encoding — Choose how your text is read into bytes (UTF-8 by default; UTF-16, Hex, Base64 and other charsets).
- HMAC — Enable keyed hashing with a secret key for message authentication.
Common uses
- A modern, structurally different alternative to SHA-2 for integrity and signatures.
- Protocols that specifically require SHA-3 / Keccak.
- Resisting length-extension attacks without extra constructions like HMAC.
Frequently asked questions
How is SHA-3 different from SHA-2?
SHA-3 uses the Keccak sponge construction — a completely different design — and resists length-extension attacks.
Is SHA3-256 secure?
Yes. It is a current NIST standard with no known practical attacks.
How long is a SHA3-256 hash?
256 bits — 64 hexadecimal characters.
Is SHA-3 better than SHA-256?
Neither is strictly better; both are secure. SHA-3 has a different design and extra resistance to length-extension attacks.