Why's that? I'm not really sure how DEFLATE works but I can imagine a crappy compression that's like "5 0" means "00000". So if you try to compress "0" you get

Why's that? I'm not really sure how DEFLATE works but I can imagine a crappy compression that's like "5 0" means "00000". So if you try to compress "0" you get "1 0" which is longer than the input. In fact, I bet this is true for any well-compressed format. Like zipping a JpegXL image will probably yield something larger. Much larger.. I don't know how you do that.