Overview
MD5 and SHA-256 are both cryptographic hash functions, but they were designed in different eras and offer vastly different levels of security. MD5 was published in 1991 by Ron Rivest as an improvement over MD4. SHA-256, part of the SHA-2 family, was designed by the NSA and published by NIST in 2001.
While MD5 was once the go-to hashing algorithm, known vulnerabilities have rendered it unsuitable for security applications. SHA-256 is now the industry standard for digital signatures, TLS/SSL certificates, and cryptocurrency. Understanding the differences helps you choose the right tool for your specific needs.
Comparison Table
| Feature | MD5 | SHA-256 |
|---|---|---|
| Year Published | 1991 | 2001 |
| Output Length | 128 bits (32 hex chars) | 256 bits (64 hex chars) |
| Internal Rounds | 4 rounds (64 operations) | 64 rounds |
| Block Size | 512 bits | 512 bits |
| Speed | Faster | Slower (more rounds) |
| Collision Resistance | Broken | No known attacks |
| Security Status | Deprecated for security | Industry standard |
| Use Cases | Non-security checksums, legacy systems | Certificates, blockchain, passwords, digital signatures |
Why MD5 Is Considered Broken
In 2004, researchers demonstrated practical collision attacks against MD5, meaning they could generate two different inputs that produce the same hash. By 2008, researchers used MD5 collisions to create a rogue CA certificate, proving the vulnerability had real-world security implications.
Today, MD5 collisions can be generated in seconds on consumer hardware. This means an attacker could create a malicious file with the same MD5 checksum as a legitimate file. For this reason, NIST, IETF, and all major security standards organizations have deprecated MD5 for cryptographic use.
Warning: Never use MD5 for password hashing, digital signatures, certificate verification, or any application where security matters.
When MD5 Is Still Acceptable
Despite its security flaws, MD5 remains useful in contexts where collision resistance is not required:
- Quick file identification: Detecting accidental corruption or identifying duplicate files in a trusted environment.
- Non-security checksums: Verifying data transfer integrity where malicious tampering is not a threat.
- Hash tables and caching: Internal data structures where the hash does not serve a security function.
- Legacy system compatibility: Interfacing with older systems that only support MD5.
When to Use SHA-256
SHA-256 should be your default choice for any application involving security:
- Password hashing: Combined with a salt and a key-derivation function like PBKDF2 or bcrypt.
- File integrity verification: Ensuring downloaded files have not been tampered with.
- Digital signatures: Code signing, document signing, and certificate verification.
- Blockchain and cryptocurrency: Bitcoin and many other blockchains use SHA-256 as their core hash function.
- TLS/SSL certificates: Modern web security relies on SHA-256 for certificate fingerprints.
See the Difference Yourself
Try hashing the same input with both algorithms using our hash generator. Notice how MD5 produces a shorter 32-character output while SHA-256 produces a 64-character output. You can also use our checksum calculator to compare file hashes side by side.