To use zLib in AutoIt, the easiest way is download the DLL, and then just use it by DllCall, or warp it by my But now I convert zLib to machine code version UDF, because "just for fun", or because I can. There is another good reason: to minimize the UDF size (because there are some functions I don't need in the DLL file). The best thing of this library is that it can compress/decompress the gzip format. So this is also a "GZIP UDF" in pure script. Example: ; ----------------------