SHA-256 Hash
Updated May 7, 2026Generate secure 256-bit SHA-256 hashes from text or files.
About SHA-256
- • Output: 256-bit (64 hex characters)
- • Security: Industry standard, no known practical attacks
- • Used in: Bitcoin, TLS/SSL certificates, file verification, digital signatures
- • Part of: SHA-2 family (SHA-224, SHA-256, SHA-384, SHA-512)
Features
- Secure SHA-256 hash generation (256-bit digest)
- Local file processing via Web Crypto API
- Standard implementation for modern cryptographic security
- Generates 64-character hexadecimal output
- Zero data upload ensures complete privacy
Common Use Cases
- Verifying the integrity and authenticity of software downloads
- Generating API signatures and authentication tokens
- Implementing secure blockchain protocols (Bitcoin uses double SHA-256)
- Hashing sensitive data for compliance (PII, email addresses)
- Creating secure digital signatures for document verification
SHA-256 (Secure Hash Algorithm 2)
SHA-256 belongs to the SHA-2 family of cryptographic hash functions, designed by the United States National Security Agency (NSA). It produces a 256-bit (32-byte) digest, typically represented as a 64-character hexadecimal string.
Currently, SHA-256 is the industry standard for most cryptographic applications. It strikes an excellent balance between security and performance.
Unlike older algorithms like MD5 or SHA-1, there are no known collision attacks against SHA-256. It is considered computationally infeasible for modern hardware to find two inputs that produce the same SHA-256 hash, making it safe for high-security applications, digital certificates (SSL/TLS), and password hashing (when combined with a salt and key stretching).
Examples
Input: "hello world"
SHA-256: b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9Input: "" (empty)
SHA-256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855Frequently Asked Questions
In practical terms, yes. Currently, no attack exists to find collisions or pre-images for SHA-256. The number of possible SHA-256 hashes is 2256, which is roughly comparable to the number of atoms in the observable universe. However, as quantum computing advances, the security margins of 256-bit hashes may be reduced, which is why some highly sensitive systems are moving to SHA-512 or SHA-3.
Bitcoin uses SHA-256 extensively. Proof-of-Work mining involves repeatedly hashing a block header with a random number (nonce) until the resulting SHA-256 hash begins with a specific number of zeroes. Bitcoin actually applies the algorithm twice (SHA256(SHA256(data))) as an added security measure against length-extension attacks.
Raw SHA-256 is not recommended for password storage because it is extremely fast. Attackers can compute billions of SHA-256 hashes per second using modern GPUs, making dictionary attacks easy. Instead, use algorithms designed specifically for passwords like bcrypt, Argon2, or PBKDF2 (which can use SHA-256 internally but runs it thousands of times to intentionally slow down attackers).
💡 Tips
- When comparing SHA-256 hashes provided by software vendors (like Docker image digests or Linux ISO checksums), ensure your tool or script handles case-insensitivity, as some vendors use uppercase hex while others use lowercase.
- If you are hashing data for compliance reasons (like masking user emails for analytics), ensure you append a secret "salt" to the string before hashing to prevent reverse-lookups via rainbow tables.