Hash Identifier
Identify hash algorithm type from hash string length and format including MD5, SHA-1, SHA-256, bcrypt, and more.
What Is a Hash Identifier?
A hash identifier guesses the algorithm behind a digest by checking string length, character set, and known prefixes. Hashes are fixed-length fingerprints of data used for password storage, file integrity checks, and digital signatures.
How Hash Length Identifies the Algorithm
Most cryptographic hashes are written as hexadecimal strings. Each pair of hex characters represents one byte, so a 32-character string is 16 bytes (128 bits), which matches MD5 and NTLM. SHA-1 uses 40 hex characters (20 bytes), SHA-256 uses 64 (32 bytes), and SHA-512 uses 128 (64 bytes).
Password hashes often include algorithm markers. bcrypt strings start with $2a$, $2b$, or $2y$. Argon2 hashes start with $argon2. Unix crypt variants use prefixes like $1$, $5$, and $6$.
Why Length Alone Is Not Enough
Several algorithms share the same digest size. MD5 and NTLM both produce 128-bit output. SHA-1 and RIPEMD-160 both produce 160-bit output. Use context, source system, and additional metadata when possible.
Related tools: MD5 Hash Generator, SHA-2 Hash Generator, and Argon2 Hash Generator.
Frequently Asked Questions
How do I identify an MD5 hash?
An MD5 hash is exactly 32 hexadecimal characters with no prefix. That equals 128 bits or 16 bytes. NTLM hashes share the same length, so check the source if both are possible.
What does a bcrypt hash look like?
bcrypt digests start with $2a$, $2b$, or $2y$ and include cost factor and salt in the string. They are much longer than a plain MD5 or SHA digest.
Can I reverse a hash to get the original text?
No. Cryptographic hash functions are one-way. You can only guess inputs and compare their hashes, or use lookup tables for weak algorithms.
Is hashing the same as encryption?
No. Encryption is reversible with a key. Hashing produces a fixed-size digest that should not reveal the original message.
Which hash types are recommended today?
For passwords, use dedicated functions like bcrypt, scrypt, or Argon2. For integrity checks, SHA-256 or SHA-512 are common choices. MD5 and SHA-1 are outdated for security-sensitive use.
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