Client Mod Extractor

TL;DR

This tool scans through a folder full of .jar files, identifies which ones are safe for the server, and safely copies them into a Save_For_Server_Mods folder so you can drag-and-drop them right onto your server.

The Problem I'm Fixing

If you are a Minecraft server owner, you probably know the pain of downloading or creating a big modpack to put on your server, only to realize that half of the mods in the folder are "Client-Side Only" (mods that only change things on your screen, like menus or sounds). If you drop those client-side mods onto your server, your server will either instantly crash, or crash later when the client-only code tries to run on the server.

Features

• Cross-Platform: Works on Windows, Mac, and Linux out-of-the-box (requires Java to be installed, which you already have if you play Minecraft).
• Smart Cloud Library: Automatically connects to GitHub to check massive lists of known "problematic" mods that have mislabeled themselves, falsely claiming to be server-safe.
• Offline Mode: If you don't have internet access, falls back to a local list of exclusions.

---

How to Use

Step 1: Download

1. Locate the Releases section on the right side of this GitHub page.
2. Click on the latest version number (e.g., v1.0.1).
3. Scroll down to the Assets heading. (Do not click "Source code" or "Assets")
4. Click Client-Mod-Extractor.zip to download it.

Step 2: Setup

1. Extract the downloaded .zip file.
2. Open your Minecraft mods folder where your .jar files are currently located.
3. Move the extracted files (ClientModExtractor.java, Run-Extractor-Windows.bat, and Run-Extractor-Linux.sh) directly into that mods folder.

Note: Ignore the ADVANCED_REVERSE_TOOL folder unless you specifically know what it is for.

Step 3: Run

1. Double-click the launcher script for your operating system:
   • Windows: Run-Extractor-Windows.bat
   • Linux / Mac: Run-Extractor-Linux.sh
   • Note for Windows users: If Windows displays a "Security Warning" or "Windows protected your PC" prompt, uncheck "Always ask before opening this file" and click Run, or click More info followed by Run anyway.
2. Wait for the terminal window to process the files.
3. Open the newly created Save_For_Server_Mods folder.
4. The .jar files inside Save_For_Server_Mods are... wait for it... safe for servers. Move these files to your server's mods folder.
5. You can leave ClientModExtractor.java and the .bat/.sh files in your mods folder— Minecraft won't touch them— but you should probably delete the Save_For_Server_Mods folder once you're done, since it's full of .jar files.

---

Technical Breakdown

Because Minecraft modding has multiple ecosystems, the script uses different methodologies to identify client-only mods depending on the modloader.

The script reads the .jar files as standard ZIP archives and analyzes their metadata files:

Fabric

1. Locates fabric.mod.json.
2. Parses the JSON structure.
3. Identifies the mod as Client-Only if it contains "environment": "client".

NeoForge & Forge

1. Locates META-INF/neoforge.mods.toml (for NeoForge) or META-INF/mods.toml (for Forge).
2. Dependency Striping: To prevent false positives, the script intelligently slices the TOML file and ignores everything after the first [[dependencies or [[mixins block. This ensures that if a mod depends on a client-side mod (like flywheel), it isn't incorrectly flagged as client-only itself.
3. Checks the core mod properties for any of the following tags:
   • clientSideOnly = true
   • side = "CLIENT"
   • displayTest = "IGNORE_SERVER_VERSION"

Dynamic Cloud Exclusions

The script reaches out via standard HTTP GET requests to fetch community-maintained blocklists (such as the itzg docker-minecraft-server JSON lists) and my own custom exclusion list. It extracts the JSON arrays using regex and builds a unified Hash Set of blocked mod IDs. Any mod that matches these IDs is skipped, even if its internal metadata claims it is server-safe.