You might think that data compression is a solved problem, lossless or lossy. But, no. Gzip and related formats like zlib, Zip, and PNG that use the DEFLATE algorithm were great 25 years ago, still do a decent job, and are completely ubiquitous and indispensable, but there are better, smarter algorithms now.
Google has announced two new compression formats in the last couple of years, Zopfli and Brotli. Zopfli does a better job of generating Deflate-compatible data, although it’s very slow. Brotli gives ~20% better compression than Deflate, but at about the same speed. Then there’s xz, which grew out of 7-zip, and also works well.
Zstandard has just been announced by Facebook and it sounds like it does a great all-round job of achieving high compression ratios at high speed. The announcement article is worth reading.
There are also several new lossless image compression algorithms: FLIF, BPG, and WebP, all of which outperform the venerable PNG.