Wirebook › Glossary › Lossless compression
What is lossless compression?
In one sentence: Packing that shrinks a file and can unpack the exact original, like a zip file.
A little more
Lossless compression shrinks a file by writing a shorter recipe for the same bytes: repeated letters become a count, repeated words go into a dictionary. When you unpack, you get the exact original back. Zip, gzip, PNG and FLAC all work this way.
It only helps when there is a pattern to fold. A letter full of ordinary English shrinks well; a file that is already packed, or a stream of genuine randomness, often stays the same size or grows by a few header bytes.
It's a bit like… Rolling clothes so they take less room in a suitcase — unfold them and every item is still there.
See it in action
- BonusWhy does zipping photos barely make them smaller?Guess which four suitcase items will squash — a repeating chorus, a letter, a camera photo and TV snow — then pack them with a real (tiny) compressor and see.7 min · interactive
- BonusWhat happens when you squish a video too much?Squish a real (tiny) picture the way phones squish video: watch thin whiskers crumble first, then 8x8 blocks appear, then a splat.10 min · interactive