SHA3-256 hash generator.

SHA3-256 is the 256-bit member of SHA-3, the standard NIST published as FIPS 202 in 2015 after a five-year public competition won by Keccak. It gives the same 64-hex-character digest length and the same 128-bit security as SHA-256 from an entirely different design, a sponge rather than a Merkle–Damgård chain.

SHA-3 is a sponge. A 1600-bit state absorbs the input a block at a time, running the Keccak-f permutation (24 rounds) after each block, then squeezes the digest out of the first part of the state. The part never exposed, the capacity, is twice the digest length, which is what sets the security level. The state is never fully output, so there is no length-extension attack, unlike SHA-2.

Yes, with a larger margin than most: the best attacks reach a handful of its 24 rounds. Because a sponge never exposes its full state, SHA3-256 is also immune to length extension, so H(key || message) is safe with it where it is not with SHA-256. NIST calls SHA-2 and SHA-3 equally approved.

Equal security, different design. SHA-256 is faster in software and has hardware instructions on most CPUs; SHA3-256 is two to three times slower in software but simpler in hardware and immune to length extension. SHA-3 exists so a break in SHA-2's structure would not take every hash down with it.

Only in the padding. NIST appended two bits to the message before the Keccak padding when it standardised SHA-3 in 2015, so SHA-3 digests differ from the original Keccak's for every input. Ethereum adopted Keccak-256 before the change and kept it, so what Solidity calls sha3 or keccak256 does not match SHA3-256. This tool gives you both families; pick the one the other side uses.

Nothing leaves your browser. The hash is computed on your machine, by the browser's Web Crypto API or a WebAssembly build of the algorithm loaded on first use, and the page makes no request with your input. You can load the page, go offline and keep hashing.

Drop the file onto the input or choose it with the button, and the tool reads it in your browser and hashes the bytes. Files up to 1 GB work; past that the browser would need the whole file in memory, so the tool declines. Paste the published digest into the Verify field to compare.

Hex is the common form: 64 characters from 0 to 9 and a to f, the same value in upper or lower case. Base64 writes the same 32 bytes in fewer characters, and Base64url swaps + and / for - and _ with no padding. Switch the output and the digest is re-encoded, not recomputed.

Text is hashed as UTF-8 bytes, which is what every language and command line does by default. A trailing newline changes the digest, so `echo -n` or this tool's input, with no newline added, matches a command-line tool run on a file without one.

Turn on HMAC and enter the secret: the tool computes HMAC-SHA3-256 over the input with that key, the standard RFC 2104 construction, so the value matches what a server-side HMAC library produces. The key is hashed as UTF-8 text.

No. The SHA3-256 hash generator is free and opens without a sign-in, an account or an install.

Nothing. The SHA3-256 hash generator holds your input in the page's memory, so closing or reloading the tab clears it, and it saves nothing in this browser.

The toolbar switches to SHA3-224, SHA3-384, and SHA3-512 without leaving the page. Each one reads the same input, so you can compare digests side by side.

SHA3-256 is computed by a WebAssembly build from the hash-wasm library, which the page loads the first time you hash something and reuses after that.

Yes: the File to SHA3-256 page has the same algorithms and options and opens on the file pane. Files are read in your browser and never uploaded.

Not on its own. SHA3-256 is built to be fast, and fast hashes are cheap for an attacker to guess against. Passwords need a salted, deliberately slow hash: use Argon2id, Argon2d, and bcrypt from the hash generators, which draw a fresh random salt each time.

Closest to the SHA3-256 hash generator: File to SHA3-256, SHA-256 hash generator, Keccak-256 hash generator, BLAKE3 hash generator. Each opens on its own page, free and in the browser.

The SHA3-256 hash generator is one of 64 in its group. The group's page, /tools/hash, lists them all.

The tool is free. Its interface is built from shadcn.io's own components (Button, Input, Slider and the rest of the registry under /ui), which come in React, Vue, Svelte and Solid. Pro adds the blocks and templates for the product around it.