What is MD5?

Ever heard of MD5 and not sure what it was or what that meant? You’re likely not alone, but MD5 is important, and, with a little explaining, easy to understand. Let’s explain a bit about MD5, MD5 checksums, what it is, and why you should know about it.

What is MD5?

MD5 stands for ‘Message Digest algorithm 5’, and for most applications, MD5 represents something like a digital fingerprint so that you can be sure a file is exactly the same whether it is stored here, there, or anywhere. It’s a very effective way ensure a digital signature and file integrity.

So why use MD5?

If you’ve ever downloaded a large file, you probably want to be sure that the file wasn’t corrupted in the process. This is particularly true with things like disk images, where using a corrupt ISO to install software can lead to disaster (I once used a corrupted ISO file to attempt a Linux install, bad idea). Using the MD5 Hash, you can be sure that the file you have on your machine is digitally identical to the original file from the source. Many sources of large files will offer an MD5 Hash to compare your file to so that you can be sure the file has transferred completely and without any molestation.

Why are you telling us about MD5?

Recently I made a post about how to check MD5 hash on Mac OS X and the first question I got from a friend of mine was ‘what the heck is MD5?’ so basically that told me an explanation of MD5 and it’s common use may be helpful to our readers. As a Mac user, I use MD5 hash’s all the time to check large file integrity, and it’s just good computing knowledge to have. Hope this helps!

For practical uses, check out how to check MD5 hash on your Mac, it works the same on Linux and Unix by the way, so you’ll be developing your command line skills all around.