SHA-256 Hash Calculator

What is SHA-256?

SHA-256 (Secure Hash Algorithm 256-bit) is a cryptographic hash function belonging to the SHA-2 family, designed by the NSA and published by NIST in 2001. It produces a fixed 256-bit (32-byte) hash value, typically rendered as a 64-character hexadecimal string.

How does SHA-256 work?

SHA-256 processes input in 512-bit blocks. The message is first padded so its length is congruent to 448 mod 512, then the original length is appended as a 64-bit integer. Each block passes through 64 rounds of operations using logical functions (Ch, Maj), modular addition, and bitwise right-rotation with eight working variables initialised from fixed constants. The outputs of all rounds are combined into the final 256-bit digest.

What is SHA-256 used for?

SHA-256 is widely used for file integrity verification, digital signatures, TLS/SSL certificates, code signing, and blockchain proof-of-work (notably Bitcoin). It is the recommended hash function for most security-critical applications and is a cornerstone of modern cryptographic infrastructure.

Can SHA-256 be reversed or cracked?

SHA-256 is a one-way function: there is no mathematical inverse. Unlike MD5 or SHA-1, no practical collision or preimage attacks have been demonstrated against SHA-256. Brute-forcing a 256-bit hash is computationally infeasible with current or foreseeable technology. For short or common strings, precomputed rainbow tables could theoretically recover inputs, but the 256-bit output space makes this vastly harder than with weaker algorithms.

Is SHA-256 safe for passwords?

SHA-256 is cryptographically secure and free of known vulnerabilities, but it is not ideal for password hashing on its own because it is designed to be fast — which benefits brute-force attackers. For password storage, use a purpose-built, deliberately slow hashing algorithm such as bcrypt, scrypt, or Argon2, which incorporate salting and adjustable work factors.

How does SHAFile ensure privacy?

SHAFile performs all hashing entirely inside your browser using the Web Crypto API (SubtleCrypto.digest). No text, no file data, and no hash output is ever transmitted to any server. You can verify this by running the tool while offline — it will work identically.