# Forge Crashes / Fabric Mods – Install Mods on Minecraft Server

Forge crashes on start or Fabric mods won't load? Mod loader, Fabric API, dependencies & mod rejections – guide with error table.

This guide shows you step by step how to install mods on your Minecraft server. We cover the two most common modloaders: Forge and Fabric. Mods add new blocks, creatures, dimensions and game mechanics to your server.

**Note:** Detailed subpages on individual modpacks and performance optimization can be found in the left navigation.

## Important difference: Forge vs. Fabric

    
        Feature
        Forge
        Fabric
    

    
        Mod selection
        Larger, more established mods
        Growing, many performance mods
    

    
        Performance
        Worse (more overhead)
        Better (leaner)
    

    
        Known modpacks
        All the Mods, FTB, Tekkit
        Better MC, Vanilla+ Packs
    

    
        Compatibility
        Only Forge mods
        Only Fabric mods
    

Mods are not cross-compatible. A Forge mod won't run on Fabric and vice versa. Choose the modloader based on the mods you want to use.

## Requirements

    - A running Minecraft server (Vanilla)
- SSH or FTP access to the server
- Java 17 or newer (for Minecraft 1.18+)
- Sufficient RAM – at least 4-6 GB with mods, 8 GB recommended
- A backup of your world (in case something goes wrong)

## Method A: Install Forge

### Step 1: Download Forge Installer

    - Visit the official Forge website: [files.minecraftforge.net](https://files.minecraftforge.net)
- Select the Minecraft version your server uses
- Download the **Installer** (not the "Universal" JAR)

### Step 2: Install Forge Server

`# In your server directory
cd /path/to/your/minecraft-server

# Run Forge installer (Java 17+ required)
java -jar forge-*-installer.jar --installServer`
The installer creates the following files:

    - **forge-xxx-universal.jar** – The new server JAR
- **mods/** – The mod folder (created automatically)
- **libraries/** – Required libraries

### Step 3: Adjust startup script

Replace your old startup script. Instead of `java -jar server.jar` use:

`java -Xmx8G -Xms4G -jar forge-xxx-universal.jar nogui`
Adjust `-Xmx8G` to your available RAM. Never start below 4 GB with mods.

### Step 4: Install mods

    - Download mods from trusted sources:
        
            - [CurseForge](https://curseforge.com/minecraft) – Largest mod platform
- [Modrinth](https://modrinth.com) – Open-source alternative

    
- Download the **.jar** files of the mods
- Upload them to the `mods/` folder on your server
- Restart the server – the mods are loaded automatically

## Method B: Install Fabric

### Step 1: Download Fabric Installer

    - Visit the official Fabric website: [fabricmc.net/use/server](https://fabricmc.net/use/server/)
- Select the Minecraft version
- Download the **Server JAR**

### Step 2: Start Fabric Server

`# In your server directory
cd /path/to/your/minecraft-server

# Rename Fabric server JAR
mv fabric-server-launch.jar server.jar

# Start server
java -Xmx8G -Xms4G -jar server.jar nogui`
Fabric automatically creates the `mods/` folder on first start.

### Step 3: Install Fabric API (important!)

Almost all Fabric mods require the **Fabric API** as a foundation:

    - Download the Fabric API from [CurseForge](https://curseforge.com/minecraft/mc-mods/fabric-api) or [Modrinth](https://modrinth.com/mod/fabric-api)
- Upload the JAR file to the `mods/` folder
- The Fabric API must always be first in the folder

### Step 4: Install additional mods

    - Download more Fabric mods from CurseForge or Modrinth
- Upload the JAR files to the `mods/` folder
- Restart the server

## Essential mods every server should have

### Performance mods (Fabric)

    - **Lithium:** Massively optimizes server performance – 40-50% less CPU load
- **Phosphor / Starlight:** Optimizes light calculation – faster chunk loading
- **FerriteCore:** Reduces RAM usage

### Performance mods (Forge)

    - **Rubidium:** Forge port of Sodium – better performance
- **Radium Reforged:** Forge port of Lithium
- **Canary:** Optimizes many server systems

## Keep mods in sync between client and server

Players joining your server must have **exactly the same mods** installed. Exceptions:

    - Server-side mods (like Lithium) only need to be installed on the server
- Client-side mods (like Sodium) only need to be installed by the player
- Mods that add new blocks/items must be installed on **both** sides

## Common problems and solutions

**Server won't start after mod installation:**

    - Check the server logs: `logs/latest.log`
- Missing dependencies? Many mods require other mods as a foundation
- Wrong modloader version? A Forge mod won't run on Fabric
- Wrong Minecraft version? A 1.19 mod won't run on 1.20

**Players cannot join ("Mod rejections"):**

    - Player has different mods or different mod versions than the server
- Solution: Distribute the same mods with the same versions to all players

**Server lags after mod installation:**

    - Too many or too resource-intensive mods
- Install performance mods like Lithium or Starlight
- Increase RAM – with many mods, 8-12 GB is often necessary

*Detailed guides on individual modpacks and performance optimization can be found in the articles in the left navigation.*