First, download AutoHotkey_sc_bin_min_size.zip. Place the extracted file, AutoHotkeySC.bin, to your AutoHotkey Compiler installation directory, commonly "C:\Program Files\AutoHotkey\Compiler\", overwriting the existing file.

It says that it will reduce the size for about 20 kB only but not all the time. Sometimes it reduces about 300 kB.

Any compiled script produced in this fashion will be dependent on MSVCRT.dll. Although this DLL is always present on Windows 2000/XP or later, older operating systems do not necessarily have it.