SHA-256 (Secure Hash Algorithm 256-bit) is a cryptographic hash function in the SHA-2 family, standardised by NIST. It produces a 256-bit (64-character hexadecimal) digest. It has no known practical collision attacks and is the current standard for security-sensitive applications.

What is SHA-256 used for?

SHA-256 is used in digital signatures, TLS/SSL certificates, Bitcoin's proof-of-work algorithm, password hashing (as part of PBKDF2), HMAC authentication, and file integrity verification.

What is the difference between SHA-256 and SHA-512?

SHA-512 produces a 512-bit digest (128 hex characters) and has a larger security margin than SHA-256. SHA-256 is faster on 32-bit systems; SHA-512 can be faster on 64-bit systems. Both are considered secure — use SHA-256 unless you have specific reasons for the larger digest.

What is SHA-256?

SHA-256 (Secure Hash Algorithm 256-bit) is the current standard cryptographic hash function. It produces a 64-character hexadecimal digest and has no known practical collision attacks.

Output

SHA-256 of hello produces: 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824 — always 64 hex characters regardless of input size.

Where SHA-256 Is Used

TLS/HTTPS certificates — certificate signatures use SHA-256
Digital signatures — signing the hash of a document
Bitcoin — double SHA-256 is used in the proof-of-work algorithm
Password hashing — as part of PBKDF2 and scrypt
HMAC authentication — HMAC-SHA256 signs API requests
File integrity — verifying downloads haven't been tampered with

SHA-2 Family

SHA-2 includes SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, and SHA-512/256. SHA-256 is the most widely deployed. All are considered secure. SHA-3 is a separate, newer family using a different algorithm (Keccak).

Generate SHA-256 hashes (and MD5, SHA-1, SHA-512): Open Hash Generator →

Frequently Asked Questions

Is SHA-256 the same as SHA-2?

SHA-256 is one member of the SHA-2 family. SHA-2 is the family name; SHA-256 specifies the 256-bit variant.

Can SHA-256 be reversed?

Not feasibly. SHA-256 is a one-way function with no known practical reversal method. Unlike MD5, it has no known collision attacks.

Related Terms

MD5 — The older, broken algorithm SHA-256 replaced.
Hash Functions — The category SHA-256 belongs to.