Installing Minecraft Mods on Your Server

Mods vs Plugins

Mods modify the game on both the server and client. Every player must install the same mods to join. This is different from plugins (used on Paper/Spigot), which run server-side only.

Feature	Mods	Plugins
Server-side only	No (requires client mods)	Yes
Platform	Forge or Fabric	Paper, Spigot, Purpur
New blocks/items	Yes	No
New dimensions	Yes	No
Client install required	Yes	No
Typical RAM usage	Higher	Lower

See Server Types Compared for the full platform comparison.

Installing Mods via the Marketplace (Recommended)

The easiest way to install individual mods on your server — no manual downloads or uploads needed:

1. Open the RespawnHost panel and select your server
2. Navigate to the Marketplace tab
3. Browse available mods or search by name
4. Click Install on the mod you want
5. The mod is downloaded automatically and placed in the correct directory
6. Restart the server to activate the mod

The Marketplace automatically checks compatibility with your server version and mod loader.

Installing Modpacks with the One-Click Installer

Modpacks bundle dozens or hundreds of mods together, pre-configured and tested for compatibility. With the One-Click Installer in the panel, you can install complete modpacks without any manual steps:

1. Open the RespawnHost panel and select your server
2. Navigate to the Modpacks tab
3. Choose from hundreds of available modpacks (CurseForge, Modrinth, FTB and more)
4. Click Install
5. The modpack is fully installed — including all mods, configs and dependencies
6. Restart the server

The One-Click Installer ensures all versions are compatible and saves you from manually tracking down individual mods.

Choosing a Mod Loader

Forge

Forge is the established mod loader with the largest mod ecosystem. Most large modpacks and complex mods (Create, Mekanism, Botania) target Forge.

Choose Forge when:

• You want to run a large CurseForge modpack
• Your preferred mods are Forge-only
• You need mature modding APIs for complex interactions

Fabric

Fabric is a lightweight, modern mod loader. It updates to new Minecraft versions quickly and has a growing ecosystem.

Choose Fabric when:

• You want fast updates to new Minecraft versions
• You prefer lightweight or performance-focused mods
• Your mod list is smaller and more focused

Version Matching

Version matching is the most common source of errors when setting up a modded server. Three versions must align:

1. Minecraft version (e.g., 1.20.4)
2. Mod loader version (e.g., Forge 49.0.26 for 1.20.4)
3. Mod version (e.g., Create 0.5.1f for Forge 1.20.4)

Every mod must be compiled for the exact Minecraft version and mod loader you are running. A mod built for Forge 1.20.1 will not work on Forge 1.20.4.

How to Verify Compatibility

• Check each mod’s download page on CurseForge or Modrinth for supported versions
• Read the mod’s changelog for version requirements
• Start with a small set of mods and add more gradually
• For modpacks, use the modpack’s bundled versions — do not mix and match

Installing Forge Mods

Server Setup

1. Set your server type to Forge in the RespawnHost panel
2. Select the Minecraft version and Forge build number
3. Start the server once to generate the /mods folder
4. Stop the server

Installing Mods

1. Download each mod .jar from CurseForge or Modrinth
2. Upload all .jar files to the /mods directory via the file manager or SFTP
3. Ensure every mod has a server-side component (some mods are client-only)
4. Restart the server

Client Setup

Every player must install the same mods:

1. Install the Forge client launcher for the matching version
2. Download the same mod files
3. Place them in the .minecraft/mods folder
4. Launch Minecraft with the Forge profile

Installing Fabric Mods

Server Setup

1. Set your server type to Fabric in the RespawnHost panel
2. Select the Minecraft version and Fabric loader version
3. Start the server once to generate the /mods folder
4. Stop the server

Installing Mods

The process is identical to Forge:

1. Download each Fabric mod .jar from Modrinth or CurseForge
2. Upload to the /mods directory
3. Restart the server

Client Setup

1. Install the Fabric Loader client
2. Download the same mod files
3. Place them in .minecraft/mods
4. Launch with the Fabric profile

Installing Modpacks Manually

If your preferred modpack is not available in the One-Click Installer, you can install it manually:

CurseForge Modpacks

CurseForge is the largest modpack platform. Most popular modpacks (FTB, All The Mods, Better Minecraft) are available here.

Server installation:

1. Download the server files package from the modpack page
2. Upload the contents to your server’s root directory
3. Follow the modpack’s included README for any additional setup steps
4. Start the server

Modrinth Modpacks

Modrinth offers a growing collection of modpacks with a modern interface. Many are also available on CurseForge.

Server installation:

1. Export or download the modpack’s server files
2. Upload to your server
3. Start and verify all mods load correctly

Tip: Check the One-Click Installer in the panel first — most popular modpacks are available there with zero manual effort.

server.properties for Modded Servers

Some properties deserve extra attention for modded setups:

# Increase max players cautiously with mods
max-players=20

# Reduce view distance for modded servers
view-distance=8
simulation-distance=4

# Keep online-mode true for security
online-mode=true

# Increase network compression if players report chunk issues
network-compression-threshold=256

Modded servers use more RAM and CPU per player. Reduce view distance and simulation distance compared to vanilla setups. See RAM Requirements for modded server memory recommendations.

Common Errors and Fixes

Mixin Conflicts

Mixin apply error modname.mixins.json:ClassName -> net.minecraft.Class

Mixin conflicts occur when two mods modify the same game code. Fixes:

• Update both mods to their latest versions
• Check the mod’s issue tracker for known conflicts
• Remove one of the conflicting mods
• Try an alternative mod that provides similar functionality

Dependency Errors

Missing required dependency: modname requires othermod version X.Y

Some mods depend on library mods (e.g., Cloth Config, Architectury, GeckoLib). Fixes:

• Read the mod’s requirements on its download page
• Download and install all listed dependencies to /mods
• Ensure dependency versions match

ID Conflicts

Block ID conflict: mod1:block1 and mod2:block2 both use ID 1234

Rare in modern Minecraft but possible with very large modpacks. Fixes:

• Remove one of the conflicting mods
• Check if a newer version resolves the conflict
• Some modpacks include ID-fix mods

Server Crashes on Startup

1. Check the crash report in /crash-reports/
2. The report identifies which mod caused the crash
3. Update or remove the offending mod
4. Search the mod’s issue tracker with the error message

JVM Memory Issues

java.lang.OutOfMemoryError: Java heap space

Your server needs more RAM. See RAM Requirements for recommendations based on your mod count.

Performance Tips for Modded Servers

• Use Minecraft Server Hosting with sufficient RAM for your modpack
• Pre-generate chunks with Chunky before opening to players
• Install Spark to identify performance bottlenecks
• Reduce entity-related settings if the modpack adds many new entities
• Consider Lithium and FerriteCore (Fabric) for server-side performance without gameplay changes

See Optimizing Server Performance for detailed tuning instructions.

FAQ

Can I mix Forge and Fabric mods?

No. Forge and Fabric are incompatible mod loaders. You must choose one or the other. Some mods have versions for both loaders, but they cannot run simultaneously on the same server.

Do all mods need to be installed on the server?

No. Some mods are client-side only (shaders, minimaps, UI tweaks). These do not need to be on the server. Check the mod’s documentation — it will specify if it is client-side, server-side, or both.

Can players join a modded server with a vanilla client?

No. Players must have the exact same mods installed. If a player connects without the required mods, they will be disconnected with a mod mismatch error.

How do I add or remove mods from a running server?

Stop the server, add or remove .jar files from the /mods folder, then restart. Never modify the /mods folder while the server is running.

What is a “server-side only” mod?

Some mods only need to be installed on the server. These typically add performance improvements (Lithium, FerriteCore), administrative tools, or generation features. Players can join with a vanilla client. The mod’s documentation will indicate if it is server-side only.

How do I find good modpacks?

Browse CurseForge and Modrinth by popularity and category. Read reviews and check update frequency. Popular modpack types include tech-focused (All The Mods), magic/adventure (Roguelike Adventures and Dungeons), and performance-optimized (Fabulously Optimized for Fabric).

Can I create my own modpack?

Yes. Start with a small set of compatible mods, test thoroughly, then distribute the mod list or exported modpack to your players. Tools like CurseForge’s modpack creator can help package everything.

Why does my modded server take so long to start?

Loading hundreds of mods requires significant time for class loading, registration, and world generation setup. This is normal. Heavy modpacks can take 5-15 minutes to fully start. Once running, performance should be stable.