Play and build custom Zombies maps in Black Ops III with the Mod Tools

Black Ops III is the easiest Call of Duty to mod because Treyarch built the pipeline into Steam. Playing a custom Zombies map is a Workshop subscription, and building one starts with a free tools download. This guide covers both sides: getting a custom map running tonight, then installing the Mod Tools and compiling a first project so you know the workflow works before you invest time in a real map.

You need the Steam version of the game. Console versions have no mod support at all.

Play a custom map from the Workshop

1. Open the game's Steam Workshop page and pick a map. Filter by "Most Subscribed" to start with something well-tested.
2. Click Subscribe. Steam downloads the map into steamapps/workshop/content/311210/ in the background, and large maps can be several gigabytes.
3. Launch Black Ops III. From the main menu go into Zombies and open the Custom Games area. Subscribed maps and mods are listed there.
4. Select the map, set your options, and start. For co-op, everyone in the lobby needs the same Workshop item subscribed and fully downloaded.

If a map does not appear, close the game, check the download finished in Steam's Downloads view, and launch again. The game only scans Workshop content on startup.

Install the Mod Tools

1. In your Steam library, switch the filter to show Tools.
2. Find Call of Duty: Black Ops III - Mod Tools and install it. Expect a download well over 100 GB once the asset library is included, so make sure the drive has room.
3. After installation, launch the Mod Tools from Steam. It opens the Launcher.

The tools install into the game's own directory. Your projects will live there too, in usermaps/ for maps and mods/ for gameplay mods.

Compile your first map

Do this before designing anything. It confirms the toolchain works end to end and teaches you the three-step build cycle you will run hundreds of times.

1. In the Launcher, create a new map. Give it a lowercase name with no spaces, like zm_firsttest. Zombies maps use the zm_ prefix by convention and the Launcher's templates depend on it.
2. Choose the Zombies template. The Launcher generates a working starting room with spawns and a script skeleton.
3. Open the map in Radiant Black from the Launcher to look around, then close it without changes for now.
4. Back in the Launcher, tick Compile, Light and Link, then run the build. Compile turns the geometry into a BSP, Light bakes lighting, and Link packages everything into fast files.
5. Click Run to launch the game straight into your map.

If the game loads and you can walk around the template room, you are set up. Everything from here is Radiant and script work.

What the project folder contains

Inside usermaps/zm_firsttest/ you will find:

• map_source/, the Radiant .map files.
• scripts/zm/, your GSC and CSC scripts. The main entry script shares the map name.
• zone_source/, the .zone files that list every asset the map should include. When an asset is missing in-game, this is the first place to look.
• sound/, alias files for custom audio.

Learn the zone file early. Most beginner errors ("missing model", "material not found", a white checkerboard texture) mean the asset exists but is not listed in the zone.

Publishing to the Workshop

The Launcher can upload directly. Set a title, description and preview image, and publish. The first upload creates the Workshop item; later uploads update it in place. Publish as unlisted or friends-only until you have tested with other people, because subscribers will start playing within minutes of a public listing.

Common gotchas

• Mods and custom maps only run in custom lobbies. There is no public matchmaking with modded content.
• Do not rename a map folder after creating it. The map name is baked into scripts, zone files and the fast file names.
• A build that fails at Link with no obvious error is usually a zone file referencing an asset with a typo in its name.
• Radiant Black needs a fair amount of video memory. If it crashes on open, lower its texture quality in the preferences.
• If the game refuses to start after you delete a project, run Steam's Verify integrity of game files to remove stale fast files.
• Keep the Mod Tools updated through Steam. Old tool versions produce fast files newer game builds reject.

Where to go next

The Black Ops III page on OpenMods lists the GitHub-hosted script libraries and asset packs you can pull into a project. For a look at where the custom Zombies scene started, the World at War guide covers the older tools that shaped this one.