The Magic of ZIP Files. How They Work

ZIP files, also known as compressed or archived files, condense multiple files into a single location with the extension ZIP, reducing the overall size and making them easier to transmit. Phillip Katz invented the ZIP file in 1986, and it was first implemented with the PKZip program for Katz’s company, PKWare. Eventually, Katz’s compression method became common usage within Microsoft Windows and Apple’s Mac OS and programs like WinRAR, WinZip and StuffIt can expand them.

But how does it all work? What kind of technological magic makes files smaller while maintaining all of the information? That “magic” is actually a pretty straightforward algorithm that takes the redundant aspects of a file and breaks it into smaller parts. This is called “lossless compression“; all of the original information is retained.

The way in which a compression program works is by recognizing patterns. According to website HowStuffWorks, it’s common for languages to have redundant patterns, which is why text files are easily compressed. But the file reduction ratio depends on several factors, including the file’s type and size and how the program chooses to compress it. Images and MP3 files contain more unique information without many patterns. That’s where “lossy compression” comes in — compression programs get rid of what they deem unnecessary information.