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Source Port

GZDoom The most popular modern source port for Doom — the engine most mods are built for.

GZDoom is a free, open-source port of the Doom engine that adds hardware-accelerated rendering, advanced modding through ZScript, and broad compatibility with thousands of community mods — for Doom, Doom II, Heretic, Hexen and Strife.

ST Skulltag editorial team Updated 2026-07-02 Tested on Windows 11
We tested this
9.0 / 10 GZDoom's integrated startup launcher makes staging Freedoom files incredibly easy, while its advanced ZScript support allows complex mod packs to run seamlessly right out of the box.

// Last tested 2026-07-02 · Windows 11 · how we test

Key features

  • Vulkan, OpenGL & software renderers — runs on almost anything.
  • ZScript modding — the most powerful Doom mod scripting available.
  • Huge mod compatibility — the target engine for most modern mods.
  • True 3D-style geometry — slopes, 3D floors, dynamic lights.
  • Built-in launcher — pick your IWAD and load mods without the command line.
  • Multi-game — Doom, Doom II, Heretic, Hexen, Strife & Chex Quest.
  • Quicksave anywhere + autosaves and full options menus.
  • Free & open-source — GPL-licensed, no cost, no ads.

What is GZDoom?

GZDoom is the most widely used source port for the classic Doom engine. A source port is a modernized version of the original game’s code that lets decades-old games like Doom (1993) run natively on current operating systems, in high resolutions, with modern controls — while staying faithful to how the games actually played.

It descends from a long lineage: id Software released the Doom source code in 1997, which led to ZDoom, and GZDoom is the OpenGL/Vulkan-rendering branch of ZDoom that became the de facto standard. Where the original engine was limited to flat levels and software rendering, GZDoom adds true 3D-style geometry (slopes, 3D floors), dynamic lighting, and a full scripting language, ZScript, that modern mods are built on.

GZDoom remains a highly popular mainline port historically targeted by the vast majority of existing mods. In late 2025, the ZDoom team forked GZDoom into UZDoom (Ultimate ZDoom) as their official continuation; Christoph Oelckers continues to maintain GZDoom independently.

If you want to play almost any Doom mod made today — from subtle gameplay tweaks to total conversions — GZDoom is the port to install first. Its multiplayer-focused cousin Zandronum shares the same Skulltag-era lineage and is the choice for online play; we cover that trade-off below.

How to install GZDoom

// From zero to playing — step by step

Download the port from the official source

Grab the latest build from zdoom.org (see the download box). Unzip it anywhere — GZDoom is portable and doesn’t need an installer.

Get an IWAD (the game data)

GZDoom is just the engine — it needs a game file called an IWAD (e.g. doom2.wad). Own Doom on Steam or GOG? Copy the WAD from your game folder. Don’t own it? Use Freedoom, a free, license-clean IWAD.

Run GZDoom & pick your game

Launch gzdoom.exe. Drop your IWAD next to it (or point the launcher at it) and GZDoom lists every game it finds. Select one and you’re in.

Load a mod

Drag any .pk3 or .wad mod onto gzdoom.exe, or add it in the launcher’s file list. That’s it.

The clean startup launcher interface of GZDoom v4.14.2, showing an easy selection menu between Freedoom: Phase 1 and Freedoom: Phase 2 with a text field for adding additional custom mod parameters.
// own capture — The clean startup launcher interface of GZDoom v4.14.2, showing an easy selection menu between Freedoom: Phase 1 and Freedoom: Phase 2 with a text field for adding additional custom mod parameters.
The main title menu of Freedoom: Phase 1 running inside the GZDoom source port, displaying the classic retro-styled navigation options over the game's open-source artwork backdrop.
// license-clean FreeDoom — The main title menu of Freedoom: Phase 1 running inside the GZDoom source port, displaying the classic retro-styled navigation options over the game's open-source artwork backdrop.
The Customize Action Controls menu overlaid on active gameplay, showcasing GZDoom's extensive, deeply customizable keybinding options for advanced player movement and weapon actions.
// license-clean FreeDoom — The Customize Action Controls menu overlaid on active gameplay, showcasing GZDoom's extensive, deeply customizable keybinding options for advanced player movement and weapon actions.
Active in-game rendering within GZDoom, showing smooth crosshair overlay and stable weapon sprite perspective while navigating a large, multi-tiered outdoor environment.
// license-clean FreeDoom — Active in-game rendering within GZDoom, showing smooth crosshair overlay and stable weapon sprite perspective while navigating a large, multi-tiered outdoor environment.

GZDoom system requirements

OSWin 7+ · macOS 10.13+ · modern Linux
GPUOpenGL 3.3 or Vulkan
FallbackSoftware renderer (any GPU)
RAM2 GB min · 4 GB recommended
Disk~100 MB (engine only)
CPUAny modern dual-core

GZDoom vs other source ports

Need to pick between ports?

Short version: GZDoom handles most needs. For the full head-to-head and our ranked list, see the dedicated pages.

Best source ports →

Frequently asked questions

Is GZDoom free?

Yes. GZDoom is free and open-source software, released under the GPL. There is no cost, no trial, and no ads. You only need to legally own a game IWAD (or use the free Freedoom) to play.

Is GZDoom safe to download?

Yes, when you download it from the official source (zdoom.org or the official GitHub releases). It is open-source, so the code is publicly auditable. Avoid third-party mirrors — we link only to the official source, and we host no binaries ourselves.

Do I need the original Doom to play?

You need a Doom-engine IWAD. If you own Doom or Doom II (Steam, GOG, or the original discs) you already have it. If not, Freedoom is a free, legal, GZDoom-compatible replacement that gives you full levels to play.

GZDoom vs Zandronum — which should I install?

GZDoom for single-player and the latest mods; Zandronum for online multiplayer. They share a lineage but have diverged: GZDoom tracks bleeding-edge ZScript; Zandronum prioritises stable netcode.

ST
Skulltag editorial team
Researched by the editorial team · last hands-on 2026-07-02 · how we test

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