If you’ve ever seen hash strings like 5f4dcc3b5aa765d61d8327deb882cf99 or 9b74c9897bac770ffc029102a200c5de, you’ve already encountered MD5, SHA-1, or SHA-256.
They’re everywhere — password storage, file integrity checks, API authentication, digital signatures, cryptocurrency, and more.
But not all hashing algorithms are created equal, and some are dangerously outdated.
Here’s a clear explanation of what each algorithm does, how they differ, and which one is still safe to use.
What Is a Hash Function?
A hash function turns any input — a password, file, or message — into a fixed-length string called a digest.
A good hash function is:
- one-way (cannot be reversed)
- collision-resistant
- fast to compute
- consistent (same input → same hash)
Not all algorithms achieve this equally well.
MD5: Fast, But Completely Broken
MD5 was introduced in 1992 and was considered secure… until it wasn’t.
Today, MD5 is fully broken:
- collisions can be generated in milliseconds
- attackers can purposely craft different inputs with the same hash
- references to “MD5 password dumps” are extremely common in breaches
Example MD5 hash:
5f4dcc3b5aa765d61d8327deb882cf99
If a system is using MD5 for passwords or signatures, it’s insecure — full stop.
SHA-1: Better Than MD5, But Still Unsafe
SHA-1 lasted longer than MD5, but it was officially declared broken in 2017.
Researchers demonstrated real SHA-1 collisions that could be generated with consumer hardware.
Example SHA-1 hash:
a9993e364706816aba3e25717850c26c9cd0d89d
Major platforms like browsers, certificate authorities, and Git have migrated away from SHA-1.
In 2025, SHA-1 should be considered deprecated in all new systems.
SHA-256: The Modern Standard
SHA-256 is part of the SHA-2 family and is still considered secure today.
It provides:
- strong collision resistance
- strong preimage resistance
- no practical attacks
- widespread hardware acceleration
Example SHA-256 hash:
9b74c9897bac770ffc029102a200c5de1b8ed9d5b0c4f8347e0b3bbcf6c5aaf6
This is the algorithm used by:
- TLS certificates
- password hashing bases (before applying slow hashing like bcrypt)
- digital signatures
- blockchain technologies
- API signing mechanisms
SHA-256 is the current gold standard for general-purpose hashing.
Quick Comparison
- MD5 → broken (collisions easy)
- SHA-1 → broken (collisions proven)
- SHA-256 → secure (recommended)
If you find MD5 or SHA-1 inside your stack, replace them immediately.
But Wait — SHA-256 Alone Is Still Not Enough for Passwords
This is critical:
SHA-256 is secure as a hash function, but not secure for password storage.
Why?
Because SHA-256 is fast, and attackers can run billions of guesses per second on modern GPUs.
Instead, always use a slow hashing algorithm designed specifically for passwords:
- Argon2id (best)
- bcrypt
- scrypt
- PBKDF2 (minimum acceptable)
These algorithms intentionally slow down attackers.
Where SHA-256 Should Be Used
Use SHA-256 when you need:
- file integrity checks
- API request signing
- generating checksums
- content addressing (like Git now uses SHA-256 mode)
- cryptographic signatures
- blockchain operations
It’s perfect for these cases.
Where SHA-1 and MD5 Still Show Up (But Shouldn’t)
You’ll still see SHA-1 or MD5 in:
- legacy APIs
- compatibility layers
- old password dumps
- archived software
- outdated SSO systems
Just because they appear doesn’t mean they’re safe.
Migrating From Weak Hashes
If you discover MD5 or SHA-1 in your application:
- Stop generating new hashes immediately
- Add a migration layer
- Re-hash existing secrets using Argon2 or bcrypt
- Phase out old hashes as users log in
- Document everything
Most modern frameworks have built-in support for this type of secure migration.
Try It Yourself
You can experiment with SHA-256, encoded tokens, API generators, and more using our free tools on credential.help:
Everything runs locally in your browser and never leaves your device.
Final Thoughts
MD5 and SHA-1 served their purpose in the early days of the web, but modern security threats have far surpassed them.
SHA-256 remains a trusted standard — but even it must be used correctly.
For password storage, use Argon2 or bcrypt.
For general hashing, SHA-256 is the reliable choice moving forward.
Understanding which algorithm fits which use-case is a simple way to strengthen your security posture across every project.