zopfli is just a compressor for the standard DEFLATE (zlib) format, able to make png, gzip and zip files a bit smaller. It spends a lot more CPU time doing the

zopfli is just a compressor for the standard DEFLATE (zlib) format, able to make png, gzip and zip files a bit smaller. It spends a lot more CPU time doing the compression to achieve marginally better compression ratios (i.e. it's like "gzip -99"). It's worth it to crunch minified js and css files (and serve them as pre-compressed "content-encoding: gzip") and png files to make a popular site load a bit faster. There is no need for special decompression code, in fact that's the whole point: an unmodified DEFLATE decompressor can decompress the file, even though it is smaller than what "gzip -9" can produce. They are compressing using LZ4-HC which is a slow compressor. They compare it to something like gzip. They should compare it to something that produces gzip-compatible data but spends even more CPU time to get even better compression ratios.