ZDoom is a source port, originally based off ATB Doom and NTDoom. It has since added practically full support for Boom, Chex Quest, Heretic, Hexen and Strife; and several games have been developed specifically for it. It has added many additional features, including slopes, uncapped fps and z-clipping. The source code is maintained by Randy Heit and Graf Zahl. The most recent version is .
- Windows: 98, ME, NT, 2000, XP, Vista, or 7
- Mac OS: Mac OS X 10.4 Tiger or above; PowerPC or Intel Mac
- Linux: Kernel 2.6 series and above
- Processor: Pentium II or better