MD5 Hash Calculator

What is MD5?

The MD5 (Message-Digest Algorithm 5) is a cryptographic hash function designed by Ronald Rivest in 1991 as a successor to MD4. It produces a fixed 128-bit (16-byte) hash value, typically rendered as a 32-character hexadecimal string.

How does MD5 work?

MD5 processes input in 512-bit blocks. The message is first padded so its length is congruent to 448 mod 512, then the original length is appended as a 64-bit integer. Each block passes through four rounds of 16 operations using nonlinear Boolean functions, modular addition, and bitwise left-rotation. The outputs of all rounds are combined into the final 128-bit digest.

What is an MD5 used for?

MD5 checksums are widely used for file integrity verification — confirming that a downloaded file has not been corrupted or tampered with. Other common applications include data deduplication (quickly finding identical files), cache key generation in web applications, and non-security fingerprinting in distributed systems. Package managers and software mirrors commonly publish MD5 checksums alongside their releases.

Can MD5 be reversed or cracked?

MD5 is a one-way function: there is no mathematical inverse. However, attackers can use precomputed rainbow tables or brute-force guessing to find inputs that produce a given hash, particularly for short or common strings. For unique, high-entropy inputs (such as large files) this is computationally infeasible.

Is MD5 safe for passwords?

No. MD5 is cryptographically broken and must not be used for passwords, digital signatures, or any security-critical application. Practical collision attacks — where two different inputs produce the same hash — have been demonstrated since 2004, and deliberate collisions can now be produced in seconds. For security-sensitive applications, use SHA-256, SHA-3, or a purpose-built password hashing algorithm such as bcrypt or Argon2.

How does MD5Kit ensure privacy?

MD5Kit performs all hashing entirely inside your browser using the Web Crypto API and the SparkMD5 JavaScript library. No text, no file data, and no hash output is ever transmitted to any server. You can verify this by running the tool while offline — it will work identically.