The most used compression algorithm in the world is deflate, also known as zlib.
Deflate and zlib are basically the same algorithm but with a small important difference:
deflate RFC1951 is the pure compressed stream: no headers, just data
zlib RFC1950 is a deflate stream with a small header at the beginning and a CRC at the end
You can recognize it due to the presence of the 0x78 byte at the beginning of the compressed data
Just for the record, there is also the Gzip RFC1952 compression but it's mainly a container rather than a stream compression and it supports other algorithms, not only deflate.
Update: Working link to zlib format file format specifications, in case anyone ever wants to actually create .zlib files and not just have the pure deflated data stream. RFC 1950 ZLIB Compressed Data Format Specification version 3.3
Deflate and zlib are basically the same algorithm but with a small important difference:
deflate RFC1951 is the pure compressed stream: no headers, just data
zlib RFC1950 is a deflate stream with a small header at the beginning and a CRC at the end
You can recognize it due to the presence of the 0x78 byte at the beginning of the compressed data
Just for the record, there is also the Gzip RFC1952 compression but it's mainly a container rather than a stream compression and it supports other algorithms, not only deflate.
Update: Working link to zlib format file format specifications, in case anyone ever wants to actually create .zlib files and not just have the pure deflated data stream. RFC 1950 ZLIB Compressed Data Format Specification version 3.3