The best performance mods for a Fabric or NeoForge server

Fabric and NeoForge servers do not get Paper’s built-in optimisations — but a handful of well-known mods close most of the gap. They change how the game does its work, not what it does, so players see the same world. This guide covers the mods worth installing on the server, what each one fixes, and which popular “performance mods” do nothing at all on a server.

The safe core

These are widely used, stable, and keep Vanilla behaviour. If your server runs Fabric, install all of them that exist for your Minecraft version:

• Lithium — optimises the game’s logic: mob AI, block ticking, collisions, hoppers, chunk loading. It is the single biggest server-side win and carefully keeps Vanilla behaviour, so even technical redstone and farms work as expected. Available for Fabric, and for NeoForge on recent versions.
• FerriteCore — cuts memory use, often by hundreds of megabytes on a modpack, by de-duplicating data the game stores many copies of. Fabric, Forge and NeoForge.
• ModernFix — speeds up startup and lowers memory, especially on large modpacks where it can shave minutes off boot time. Fabric, Forge and NeoForge.

None of these need players to install anything. They are server-side; if a player has them on their own game too, that only helps their own single-player.

Worth considering

• Krypton (Fabric) — optimises the networking stack. Helps most on servers with many players; on a group of friends, the gain is small but free.
• C2ME (Fabric) — runs chunk generation and loading across several threads. Big gains on machines with many cores, small gains on two. It is more experimental than the others, and occasionally conflicts with world-generation mods, so add it last and test.
• Chunky — not an optimisation, but pre-generating the world removes the most expensive thing a server does while people play. See How to pre-generate your world.

On Forge for older versions

Older Forge versions — 1.20.1 and earlier, where many big modpacks still live — have their own set. Canary is a Forge port of Lithium for those versions; FerriteCore and ModernFix exist natively. Check each mod’s page for your exact version: ports lag behind, and a port for 1.19.2 will not load on 1.20.1.

Mods that do nothing on a server

The most famous performance mods are client mods. They make your game render faster on your PC, and the server never draws a frame:

• Sodium, Embeddium and Rubidium — rendering engines.
• Iris and Oculus — shaders.
• Entity Culling, More Culling, ImmediatelyFast and Dynamic FPS — rendering and window tweaks.

At best they are skipped at startup. At worst they crash the server because they try to load graphics code that does not exist there. Recommend them to your players instead — on a modpack they are often the difference between 30 and 120 FPS. Client mods vs server mods explains how to tell them apart.

Starlight and Phosphor are retired

Lighting mods were essential a few years ago. Since Minecraft 1.20, the Vanilla lighting engine was rewritten with the same ideas and the old mods were discontinued. On 1.20 and newer, you do not need them; on older versions they still help.

Profilers: useful, but not on every host

The spark profiler is the standard way to see exactly which mod is eating tick time. It needs low-level access to the Java process to sample it, and some hosts run servers in locked-down containers where that access is blocked. On a Cobbly free server, spark’s profiler cannot start and it crashes the server at startup, so modpack installs remove it automatically. Use the built-in tick commands instead — tick query on 1.20.3+, or neoforge tps / forge tps — which show the time per dimension.

Install them one by one

Add performance mods to a working server one at a time, starting the server after each. If one conflicts with your other mods, you will know which. Keep the version matched exactly: a Lithium built for 1.21.1 will not load on 1.21.4. How to add mods to your Minecraft server has the upload steps, and Why won’t my Minecraft server start? covers reading the error if one refuses to load.