Keccak-256 hash generator.

Keccak-256 is the 256-bit output of the original Keccak sponge, the function that won NIST's SHA-3 competition in 2012. Ethereum adopted it before SHA-3 was finalised with different padding, so Keccak-256 and SHA3-256 give different digests, and Ethereum's is this one.

Nearly everything. An address is the last 20 bytes of the Keccak-256 of the public key; transaction and block hashes are Keccak-256; Solidity's keccak256 (and its misnamed sha3) and the function selectors in every contract call (the first four bytes of the Keccak-256 of the signature) are too. EIP-55 checksummed addresses are cased by it as well.

Keccak is a sponge: a 1600-bit state absorbs the input in blocks, applying a 24-round permutation after each, then the digest is read from the first bits of the state. The capacity, the part of the state never output, is twice the digest size, and that is the security margin. No length-extension attack exists against it.

Yes: it is the same permutation as SHA3-256 with the same 512-bit capacity, so the same 128-bit security, and no attack on the full function is known. Ethereum's whole value depends on it, and it has held.

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-Keccak-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 Keccak-256 hash generator is free and opens without a sign-in, an account or an install.

Nothing. The Keccak-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 Keccak-224, Keccak-384, and Keccak-512 without leaving the page. Each one reads the same input, so you can compare digests side by side.

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

The Keccak-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.