SHA-256 vs SHA-512: Which Hash Algorithm Should You Use?

Both Are SHA-2

SHA-256 and SHA-512 are both part of the SHA-2 family, standardised by NIST in 2001. Neither has known practical vulnerabilities. The primary differences are output size and performance.

Output Size

• SHA-256: 256-bit hash → 64 hex characters or 32 bytes
• SHA-512: 512-bit hash → 128 hex characters or 64 bytes

A larger output means more collision resistance. The theoretical collision resistance of SHA-256 is 2^128 operations; SHA-512 is 2^256. Both are far beyond any feasible attack.

Performance

Performance depends heavily on the processor architecture:

On modern 64-bit desktop/server CPUs, SHA-512 is often faster than SHA-256 because its 80-round computation on 64-bit words outperforms SHA-256's 64 rounds on 32-bit words for large inputs.

Which to Choose

Use SHA-256 when:

• Compatibility with older systems is required
• The hash appears in compact formats (JWT, checksums, certificates)
• You need AES-NI paired with SHA-NI acceleration
• The target is 32-bit embedded systems

Use SHA-512 when:

• Maximum security margin is important
• Running on 64-bit servers processing large files
• Compliance requirements specify SHA-512

Use SHA-3 (Keccak) when:

• You want a completely different design lineage from SHA-2
• Resistance to length-extension attacks matters (SHA-2 is vulnerable; SHA-3 is not)

Neither Is Suitable for Passwords

SHA-256 and SHA-512 are fast — exactly the wrong property for password storage. Use bcrypt, Argon2id, or PBKDF2 for passwords.

Generate and verify hashes with our Hash Generator tool.