MD5 Hash Code Calculator

The MD5 (Message Digest Algorithm 5) is a widely used cryptographic hash function that produces a 128-bit (16-byte) hash value, typically represented as a 32-character hexadecimal number. It was designed by Ronald Rivest in 1991 and is commonly used to verify data integrity. Although it has at the time of writing not been considered appropriate for security-related purposes for several years, it seems to still see widespread use as a file integrity checker. I would suggest using one of the many better alternatives when designing new systems, though.

Full disclosure: I did not write the specific implementation of the hash function used on this page. It is a standard function included with the PHP programming language. I only made the web interface to make it publicly available here for convenience.

About the MD5 Hash Algorithm

To really understand the internals a hash function, you need to be really good at math and I'm not, at least not at this level. Therefore, I'll try to explain this hash function in a way that my fellow non-mathematicians can understand. If you prefer the more precise, math-heavy explanation, you can find that on plenty of other websites ;-)

Anyway, imagine that MD5 is some sort of super smart blender. You put any kind of food (your data) into it - like fruits, vegetables, or even a pizza - and when you press the button, it always gives you the same kind of smoothie: a 32-character "smoothie code" (the MD5 hash in hexadecimal form).

• If you put in the exact same ingredients every time, you'll get the exact same smoothie code.
• But if you change even one tiny thing (like one extra sprinkle of salt), the smoothie code will be completely different.

How Does the "Blender" Work Inside?

While it seems magical, inside the blender, MD5 is doing a lot of chopping, mixing, and spinning:

• Chop: It breaks your data into small pieces (like chopping fruits).
• Mix: It mixes the pieces using a secret recipe (math rules) that scrambles everything around.
• Blend: It spins everything super fast, mashing it into a weird code that looks nothing like the original.

No matter if you put in one word or an entire book, MD5 always gives you a 32-character code.

MD5 used to be very secure, but smart people figured out how to trick the blender. They found ways to create two different recipes (two different files) that somehow end up with the same smoothie code. This is called a collision.

Imagine someone giving you a smoothie code that says "this is a healthy fruit smoothie," but when you drink it, it's actually something completely different. That’s why MD5 is no longer safe for things like passwords or security.

Some people keep claiming that it's fine for file integrity checks and similar purposes, but one thing you really don't want in a file integrity check is a collision, because that would make the hash look like two files are the same even if they aren't. So even for non-security related matters, I highly recommend using a more secure hash function. At the time of writing, my default go-to hash function for most purposes is SHA-256.

Of course, I have a calculator for that too: SHA-256 Hash Code Calculator.