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SHA256 Generator
This SHA256 generator turns any text or file into a SHA-256 hash — a fixed 64-character fingerprint that changes completely if even one character of the input changes. Type or paste text, or drop a file onto the box, and the hash appears instantly. It runs entirely in your browser with the WebCrypto API, with a built-in JavaScript fallback for older browsers, so your text and files are never uploaded anywhere.
How the hash is built
Any input, of any length, goes through 64 rounds of mixing and comes out as exactly 64 hexadecimal characters — 256 bits. Change one letter and the whole output changes.
How it works
A hash function is a machine that turns input into a fingerprint. SHA-256, short for Secure Hash Algorithm with a 256-bit output, takes any text or file — one letter or a whole library — and produces exactly 64 hexadecimal characters. The same input always gives the same hash, and a different input gives a different hash. It is a one-way function: given only the hash, you cannot work out the original text, which is why hashes are used to store passwords and to check files.
Inside, SHA-256 works in 64 rounds. First the input is padded: a 1 bit, then zeros, then the length of the input, until the total is a multiple of 512 bits. The message is then split into 512-bit blocks, and each block is mixed into eight running values using rotations, shifts, additions, and bitwise choices. The mixing is deliberately thorough, so a change in one bit of the input spreads through every bit of the output. That spreading is called the avalanche effect, and it is the reason the hash of "hello" and the hash of "Hello" look nothing alike even though the inputs differ by one capital letter.
This tool computes the hash with the WebCrypto API, the standard cryptography library built into modern browsers. The text is encoded as UTF-8, passed to crypto.subtle.digest with SHA-256, and the resulting bytes are written out as hexadecimal. If the browser does not offer WebCrypto — for example on an older browser or a page served without a secure connection — the tool falls back to a pure JavaScript implementation of SHA-256 built into the page, so the hash still works. Both paths give the identical result for the same input.
Files are hashed the same way: the file is read as bytes in your browser and the bytes are fed to the same function, so the hash covers the exact contents of the file. That is how downloads are verified in the real world. A publisher lists the SHA-256 hash of a file next to the download link; you hash your copy and compare. If the two hashes match, the file arrived intact and unaltered. If they differ by even one character, something changed on the way — a broken download, or a file that was tampered with.
One warning: a hash is not encryption. It does not hide the input from someone who can guess it, because a guesser can hash their own guesses and compare. Short, common passwords are still weak even when hashed, which is why password systems add a random salt and use a slow hashing method for storage. SHA-256 is a checksum and a fingerprint, not a password vault.
Worked example
Hash the word "hello" with SHA-256.
Step 1: Type hello into the text box. It is 5 characters long, or 40 bits.
Step 2: The tool encodes the text as UTF-8 and passes it to SHA-256.
Step 3: The function pads the message, runs its 64 rounds of mixing, and produces 256 bits of output.
Step 4: The output is written as 64 hexadecimal characters.
Try it yourself: the tool opens with hello already typed in. Press Generate hash and the tool gives exactly the same result — 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824. Change the H to a capital and watch the whole hash change: that is the avalanche effect in action.
FAQ
What is a SHA-256 hash?
SHA-256 is a hash function that turns any input, of any size, into a fixed 64-character hexadecimal fingerprint. The same input always gives the same hash, and changing even one character gives a completely different hash. It is a one-way function: you cannot turn the hash back into the original text, which is why hashes are used to store passwords safely and to check that files have not been changed.
What is a SHA-256 hash used for?
SHA-256 is used to verify downloads, store passwords, and secure blockchains. When you download a file, the publisher often lists its SHA-256 hash, and if the hash of your copy matches, the file arrived intact. Password systems store the hash of your password instead of the password itself. Bitcoin and many other systems use SHA-256 to link blocks of data together.
Can two different inputs have the same SHA-256 hash?
In theory yes, because there are more possible inputs than possible 64-character hashes, but in practice no. Finding two inputs with the same SHA-256 hash would take about 2 to the power of 128 tries, which is far beyond any computer that exists. That is why SHA-256 is trusted for security: a matching hash is taken as proof that the input is unchanged.
Is my text sent anywhere when I hash it here?
No. The hash is computed in your browser with the WebCrypto API, or with a built-in JavaScript fallback on older browsers, and nothing is uploaded or stored. You can hash passwords, documents, or private text without worry. The only copy of the hash is the one you make with the Copy button.
Why does changing one letter change the whole hash?
That is called the avalanche effect, and it is designed into the hash function. SHA-256 mixes the input through 64 rounds of shifting, rotating, and adding, so a tiny change at the start spreads through every part of the result. The hash of hello and the hash of Hello share almost no characters in common, even though the inputs differ by a single capital letter.