What is a SHA-256 hash?

SHA-256 is a cryptographic hash function in the SHA-2 family. It takes any input of any length and produces a fixed 256-bit (32-byte) output expressed as a 64-character hexadecimal string. The same input always produces the same hash, but even a single character change produces a completely different output. It is used in digital signatures, data integrity verification, password storage and blockchain systems.

Can a SHA-256 hash be reversed?

No. SHA-256 is a one-way function: given the hash you cannot computationally recover the original input. This is what makes it useful for storing passwords and verifying data integrity. An attacker can only find the original by trying all possible inputs, which is computationally infeasible for strong inputs.

Is this hash generator safe to use?

Yes. This tool uses the browser's built-in SubtleCrypto Web API to compute hashes entirely on your device. Nothing you type is sent to any server. For sensitive data such as passwords or private keys, using a browser-based tool is significantly safer than an online tool that sends your input to a remote server.

Hash Generator (SHA-256)

A cryptographic hash function converts any input of any length into a fixed-size output called a hash or digest. SHA-256, part of the SHA-2 family standardised by NIST, produces a 256-bit (32-byte) output represented as a 64-character hexadecimal string. It has three properties that make it useful in computing: it is deterministic (the same input always gives the same output), it is fast to compute in one direction but computationally infeasible to reverse, and it has the avalanche effect (changing even one character in the input produces an entirely different hash). These properties underpin a wide range of applications: verifying downloaded files have not been corrupted or tampered with, storing password hashes in databases instead of plain text, generating digital signatures, building Merkle trees in blockchain systems, and creating message authentication codes. This tool computes the SHA-256 hash of any text you type, directly in your browser using the SubtleCrypto Web API, part of the modern Web Crypto standard. Because the computation runs locally, nothing you enter is transmitted to any server. The hash updates as you type. The default input "Hello World" produces a specific 64-character hex string you can use to verify the tool is working correctly.

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Input text

a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e

SHA-256 hash (hex)

Hash bits256

Hash characters64

Input characters11

SHA-256 only. Computed in your browser using SubtleCrypto. Nothing is uploaded or stored.

How it works

The input text is encoded to UTF-8 bytes using a TextEncoder. Those bytes are passed to window.crypto.subtle.digest('SHA-256', ...) which returns a Promise resolving to an ArrayBuffer of 32 bytes. The bytes are converted to a lowercase hexadecimal string by iterating over each byte value, calling toString(16), and padding to two characters. The result is always exactly 64 hex characters regardless of input length. Because SubtleCrypto is asynchronous, the hash is computed with a .then() callback and the display updates when the Promise resolves.

Worked example

Input "Hello World" (11 characters). SHA-256 processes the UTF-8 bytes through 64 rounds of bitwise operations and produces the 256-bit digest: a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e. This is always 64 hexadecimal characters (256 bits). This matches the default pre-filled in the calculator above.

Related calculators

Base64 Encoder/Decoder: encode or decode text using Base64.
Bitwise Calculator: AND, OR, XOR and NOT operations with binary output.
Hexadecimal Calculator: arithmetic in hexadecimal with decimal and binary equivalents.

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