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Server Setup

How to Add Mods to a Minecraft Server

Modding a server is three rules: one loader, jars in the mods folder, every client matched. Get those right and the boot log prints Loading N mods. Get them wrong and it crashes on the offending jar.

How mod loading works
  1. 1
    Pick one loader
    Choose Forge OR Fabric for the whole server. Run the matching server jar once so it builds the config and creates an empty mods folder.
  2. 2
    Get server-side jars
    Download mods built for your exact MC version and loader from Modrinth or CurseForge. On Fabric, always add Fabric API as a dependency.
  3. 3
    Drop jars in mods
    Stop the server, copy each .jar into the server's /mods folder. No nesting, no renaming, keep the .jar extension intact.
  4. 4
    Start and read the log
    Boot the server and watch the console for "Loading N mods". A missing-dependency or version-mismatch crash names the offending jar.
  5. 5
    Match every client
    Players need the same loader, same MC version, and the same client-required mods. Server-only optimizers (Lithium, FerriteCore) don't need a client copy.
server console, fabric-server-launch● running
[main/INFO]: Loading Minecraft 1.20.1 with Fabric Loader 0.15.7
[main/INFO]: Scanning mods directory...
[main/INFO]: Found 6 mod candidates
[FabricLoader/INFO]: Loading 6 mods:
- fabric-api 0.92.0+1.20.1
- sodium 0.5.3
- lithium 0.11.2
- ferritecore 6.0.1
- lazydfu 0.1.3
- modmenu 7.2.2
[Server/INFO]: Preparing level "world"
[Server/INFO]: Loading 6 mods complete
[Server/INFO]: Done (4.812s)! For help, type "help"
Steve joined the game
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What you need

Mod .jar files
/mods folder
Fabric API
Matching MC version

Quick answers

?
Forge or Fabric?
Both can't run at once. Fabric is lighter and faster to update; Forge has the deepest mod catalog. Match whatever your chosen mods are built for.
?
Where is the mods folder?
In the server's root directory, next to server.jar and world. It appears automatically the first time you launch the modded server jar.
?
Do I need Fabric API?
Almost always on Fabric. Most mods depend on it. If the log says a mod "requires fabric" then drop fabric-api.jar into the same mods folder.
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Why does it crash on boot?
Usually a version mismatch (mod built for a different MC version) or a missing dependency. The crash report names the mod and what it expects.
?
Do clients need the same mods?
Yes for content and gameplay mods. Server-side-only mods (Lithium, FerriteCore, Spark) run fine without any client install.
?
Can I use plugins too?
Not on vanilla Forge/Fabric. For Bukkit-style plugins use Paper, or run a hybrid like Mohist if you genuinely need both.
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