Eli5: How do zip files work? How do they make files just smaller?

Question

Eli5: How do zip files work? How do they make files just smaller?

In: Technology

Answer 1

The trick with a file compression algorithm is that you try to find repeating patterns in a file. And when you find a repeating pattern, instead of keeping the entire pattern again, you type in a reference to the first place in the file where that pattern occurred.

Works better, of course, if patterns have the decency to repeat themselves often. Or a least similar.