Install Lithium on your Minecraft server

Lithium is a server-side optimisation mod. It speeds up game logic such as mob AI, block ticking and physics, and its aim is to leave vanilla mechanics exactly as they are. Your players don't need to install it. The steps below add it to a Fabric or NeoForge server (or a Quilt one, where your JAR Manager offers Quilt) and check that it made a difference.

Checked against Lithium 0.26.2 for Minecraft 26.3 on Fabric and NeoForge, October 2026.

Does your server run it

Lithium has builds for Fabric and NeoForge, and the Fabric build also runs on Quilt, where your JAR Manager offers it. It doesn't have a Forge build, and it isn't a plugin, so a Paper or Purpur server can't load it (Minecraft plugins vs mods explains the split). On Paper, Why is my server lagging? is the place to start.

Check the Mods tab, under Content in the panel menu. If it's missing, open JAR Manager under More and switch to Fabric or NeoForge (Change your Minecraft version or mod loader). Switching reinstalls the server and keeps your world, but some configuration files can reset, so make a backup first in the Backups tab.

Take a baseline reading

On the Console tab, the TPS card shows ticks per second, with a target of 20. Note what it reads while players are online. Lithium's page says the gain is in tick times, which lets hardware carry more loaded entities, chunks and players. A quiet server already sitting at 20 may show little change.

For a second number, run this in the console:

tick query

It is a vanilla command in Minecraft 1.20.3 and newer, and it replies with a line such as Average time per tick, in milliseconds. A lower number is better.

Install Lithium

1. Open the Mods tab and keep the Modrinth chip selected.
2. Search for Lithium. The one you want is by jellysquid3, whose description calls it a no-compromises game logic mod. Names like "Lithium Raycast Fix" are separate mods.
3. Click Install on its row. The store picks the build for your server's Minecraft version and loader.
4. Restart from the Console tab.

Lithium needs no other mods. Its page says even Fabric API isn't required, and that your existing world benefits straight away with no need to create a new one.

Check it loaded

Open the Mods tab and click Installed. Lithium should be listed there. The Failed to load badge did not appear in our tests when a server crashed at start, so also check that the Console reaches its Done line. Then compare the TPS card and tick query with your baseline after players have been online for a while.

The config file

Lithium works with its defaults, and it shouldn't need changes. When it first starts it creates a lithium.properties file in the config folder that holds only a short comment notice and no options. A file with no options is normal: it means you want every default.

Each option can be switched off by name if another mod clashes with Lithium. Stop the server, open the file in the File Manager and add a line such as:

mixin.ai.pathing=false

Every option is listed in the project's own docs, one page for Fabric and one for NeoForge. Options only take effect after a restart, and the project asks you to back up your worlds before editing the file.

Updating

Click Check for updates in the Installed view. The store swaps in the newest build for your server's version, and you restart afterwards. Lithium publishes a separate build for each Minecraft version, so when you move the server to a new version, update Lithium to match.

Common problems

• Lithium isn't in the search results: the Game version filter starts on your server's version. If Lithium has no build for it yet, the results come back empty. Wait for the build, or stay on the older Minecraft version.
• A mod stopped working after installing Lithium: turn off the matching option in lithium.properties and restart. Lithium's page says the option system exists to remove mod incompatibilities.
• The server stops at start with "Overworld settings missing" on a server that also runs Terralith: in our test, Lithium 0.26.2 with Terralith 2.6.5 on Fabric 26.3 would not start on a new world, and adding mixin.gen=false to lithium.properties let the pair start. Each mod started fine alone.
• No change in TPS: that usually means something else is the limit. Why is my server lagging? lists the usual causes, from RAM to a mod that started the lag.