Can a hash be reversed or decrypted?

No. Cryptographic hashes are designed to be one-way functions. You cannot mathematically reverse a hash back into its original text. However, weak hashes like MD5 are vulnerable to 'rainbow table' attacks where pre-computed hashes are compared.

Is my data sent to a server to be hashed?

No. All hashing is performed locally in your web browser. Your sensitive text or files never leave your device.

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Hash Algorithm Comparison

Comprehensive comparison of MD5, SHA-1, SHA-256, SHA-512, and SHA-3. Find the right algorithm for your security needs.

Quick Recommendation

For most use cases, use SHA-256. It offers the best balance of security, performance, and compatibility. For passwords, use Argon2 or bcrypt instead.

Cryptographic Hash Functions

Algorithm	Output	Status	Speed	Use
MD5 1992	128 bits 32 chars	Broken	Very Fast	Checksums only
SHA-1 1995	160 bits 40 chars	Deprecated	Fast	Legacy systems
SHA-256 2001	256 bits 64 chars	Secure	Moderate	Recommended
SHA-384 2001	384 bits 96 chars	Secure	Moderate	High security
SHA-512 2001	512 bits 128 chars	Secure	Fast on 64-bit	High security
SHA-3 (256) 2015	256 bits 64 chars	Secure	Moderate	Future-proof

Which Algorithm for Which Use Case?

Use Case	✓ Recommended	△ Acceptable	✗ Avoid
File checksums *MD5 acceptable for non-security checksums only	SHA-256	MD5*	—
Password storage Never use plain hashes for passwords	Argon2 / bcrypt	scrypt	MD5, SHA-*
Digital signatures Required for SSL/TLS certificates	SHA-256+	SHA-384, SHA-512	MD5, SHA-1
HMAC API authentication, JWTs	SHA-256	SHA-512	MD5, SHA-1
Content addressing Git, IPFS, Docker images	SHA-256	SHA-512	MD5
Blockchain Bitcoin uses double SHA-256	SHA-256	Keccak-256	Others

Special Note: Password Hashing

Never use plain cryptographic hashes (MD5, SHA-*) for passwords. They're too fast, making brute-force attacks trivial. Use dedicated password hashing algorithms designed to be slow:

bcrypt

1999

Industry standard for password hashing. Adjustable cost factor.

Argon2

2015

Winner of Password Hashing Competition. Memory-hard.

scrypt

2009

Memory and CPU hard. Used in some cryptocurrencies.

PBKDF2

2000

Older but still acceptable. NIST recommended.

Hash Output Examples

All algorithms produce fixed-length output regardless of input size. Here's what "Hello" looks like as each hash:

MD5 (32 chars)

8b1a9953c4611296a827abf8c47804d7

SHA-1 (40 chars)

f7ff9e8b7bb2e09b70935a5d785e0cc5d9d0abf0

SHA-256 (64 chars)

185f8db32271fe25f561a6fc938b2e264306ec304eda518007d1764826381969

SHA-512 (128 chars)

3615f80c9d293ed7402687f94b22d58e529b8cc7916f8fac7fddf7fbd5af4cf777d3d795a7a00a16bf7e7f3fb9561ee9baae480da9fe7a18769e71886b03f315

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