File to SHA3-256.

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 file is read on your machine and hashed there, by the browser's Web Crypto API or a WebAssembly build of SHA3-256 loaded on first use; the page makes no request with its bytes. You can load the page, go offline and keep hashing.

Drop the file onto the pane or choose it with the button. It is read into memory and hashed at once, with no size steps and no upload progress because there is no upload. Files up to 1 GB work; a 100 MB file takes well under a second on SHA3-256.

Paste the digest the publisher gave you into the Verify field, in hex of either case, with or without spaces, colons or a 0x prefix, or in Base64. The tool says whether it matches the file you dropped. A match means the bytes are exactly the ones that were published.

Hex by default, 64 characters; Base64 and Base64url are one click away and re-encode the same 32 bytes. The download button saves a line in the `digest filename` form that sha256sum-style tools read.

Yes: turn on HMAC and enter the secret, and the file is signed with HMAC-SHA3-256 rather than hashed, the same construction a server uses to sign an upload or a webhook payload.

No. The "File to SHA3-256" tool is free and opens without a sign-in, an account or an install.

Nothing. The "File to SHA3-256" tool 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 SHA3-256 hash generator page has the same algorithms and options and opens on the text box. This page opens on the file pane.

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

The "File to SHA3-256" tool 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.