ZombieBuddy

A framework that enables advanced Java mods for Project Zomboid.

What it does: ZombieBuddy is required by some mods to work. If a mod tells you to install ZombieBuddy, follow the instructions below.

Installation (One-Time Setup)

Step 1: Subscribe to ZombieBuddy on Steam Workshop

Step 2: Installation is required ONLY ONCE for ZombieBuddy itself.

🪟 Windows:

Option A: Automated Installer (Recommended)

• Download the latest ZombieBuddyInstaller.exe from GitHub Releases
• Run the installer and choose Install or update ZombieBuddy.
• Choose what launch mode to patch:
• [list]
• Both (recommended): patches Normal Launch and Alternate Launch.
• Normal Launch: then choose ProjectZomboid64.json, Steam launch options, or both.
• Alternate Launch: patches ProjectZomboid64.bat.

[*] The installer shows every system change first and asks for confirmation before applying it. [*] If Steam launch options need to be changed, the installer will ask you to close Steam at that point. [*] The same installer can also uninstall ZombieBuddy later: run it again and choose Uninstall ZombieBuddy. [/list]

Option B: Manual Installation

• Copy ZombieBuddy.jar and zbNative.dll from:
• [code]C:\Program Files (x86)\Steam\steamapps\workshop\content\108600\3619862853\mods\ZombieBuddy\libs\[/code]
• to your Project Zomboid folder:
• [code]C:\Program Files (x86)\Steam\steamapps\common\ProjectZomboid\[/code]
• Open Project Zomboid's launch options in Steam
• Add this launch option: [code]-agentlib:zbNative --[/code]
• ⚠️ IMPORTANT: The -- at the end is mandatory - do not omit it!
• If you use the game's Alternate Launch option on Windows, set the ProjectZomboid64.bat _JAVA_OPTIONS line to: [code]SET _JAVA_OPTIONS=-agentlib:zbNative[/code]

🍎 macOS / 🐧 Linux:

• Copy ZombieBuddy.jar from the mod's libs/ directory to:
• [list]
• macOS: ~/Library/Application Support/Steam/steamapps/common/ProjectZomboid/Project Zomboid.app/Contents/Java/
• Linux: ~/.steam/steam/steamapps/common/ProjectZomboid/projectzomboid/

[*] Open Project Zomboid's launch options in Steam [*] Add this JVM argument: -javaagent:ZombieBuddy.jar -- [*] ⚠️ IMPORTANT: The -- at the end is mandatory - do not omit it! [/list]

Step 3: After this setup, all mods that require ZombieBuddy will work automatically!

Uninstall

• Disable the agent first: Open Project Zomboid → Properties → clear the Launch Options line
• Delete zbNative.dll and ZombieBuddy.jar from your Project Zomboid install directory
• Unsubscribe from ZombieBuddy on Steam

⚠️ Security Warning ⚠️

Java mods enabled through ZombieBuddy have unrestricted access to your system. Only install mods from sources you trust.

No jar will sneak in. Whenever a Java mod ships a new or updated JAR, ZombieBuddy shows a native dialog with the mod id, file path, last-modified date, and SHA-256 fingerprint. Nothing is loaded until you click Yes. You can choose to remember the decision (per-mod, per-hash) or keep it session-only. Persisted allow/deny choices are written to JSON (mod id → { sha256 → true|false }) at:

• Windows: %USERPROFILE%\.zombie_buddy\mod_approvals.json
• macOS / Linux: ~/.zombie_buddy/mod_approvals.json

If a previously-approved JAR changes on disk (hash mismatch), you will be prompted again. Tip: hold Shift during game load to force the approval dialog to appear, even for previously approved Java mods.

Java Mod Policy

Controls what happens when an unknown/changed JAR is seen. Pass as a policy=... argument:

• prompt (default) - ask me each time via a native dialog.
• deny-new - silently skip any JAR that isn't already approved.
• allow-all - load every JAR without prompting. Not recommended.

Examples (block form, these go into Steam launch options):

-agentlib:zbNative=policy=deny-new --            (Windows)
-javaagent:ZombieBuddy.jar=policy=deny-new --    (macOS / Linux)

FAQ

• Is it a virus?
• No.
• How to start game in debug mode?
• [code]
• -agentlib:zbNative -- -debug
• OR
• -javaagent:ZombieBuddy.jar -- -debug
• [/code]
• Do I need to repeat manual installation after I upgrade/downgrade/validate game?
• No, if you use the default launcher and have agentlib in Steam launch options.
• Yes, if ZombieBuddy stops loading.
• Works on MP?
• Yes.
• Save compatibility?
• Safe to add or remove on existing saves.
• I clicked the wrong button in the approval dialog. How do I reset it?
• Open mod_approvals.json (path above), under 'mods' find your mod id, then remove or edit the SHA-256 key you want to reset (or change true/false), save, and restart.
• Can I see which Java mods were loaded or blocked?
• Yes - install Zed's Better ModList and the status is shown next to each JAR path in the mod list.
• Supported game versions?
• B41, B42.12-B42.21
• Can I hide ZB watermark?
• Yes, in ModOptions. During game boot it is always visible.
• WHY ALL LINKS ARE REMOVED FROM THIS PAGE AND COMMENTS DISABLED???!!!
• Steam does that while it checks a newly uploaded mod version for viruses, I suppose. Everything should return to normal in 10..30 minutes, depending on how busy their system is.

Links

GitHub Repository