Lithium

Lithium is a performance mod created by CaffeineMC. A server-side optimization mod that improves game logic performance including entity AI, world gen, and block ticking. As a performance mod it concentrates on frame rate, loading times, and memory use, and it has been downloaded around 80 million times, which puts it among the options players reach for in this space.

Lithium is built for server owners and players who want faster ticks without changing any behaviour. It optimises the game's general logic, AI, physics, and chunk handling while staying strictly vanilla-accurate, so nothing you build behaves differently. It is approachable enough to drop into a world and use right away, with little setup required.

The mod is available for Fabric and Quilt, so it fits a range of modpacks and launchers. It currently supports Minecraft 1.20.1, 1.20.4, and 1.21.1, spanning the 1.20.1 to 1.21.1 releases. It is primarily a server-side mod, so installing it on the server applies its effects for everyone without each player needing it in their own client.

Lithium works particularly well alongside Sodium, FerriteCore, and Starlight. It targets the Fabric side of the ecosystem, so it pairs naturally with other Fabric mods and performance tools.

Lithium changes no mechanics by design, which makes it one of the safest performance mods to run on survival servers.

If you are comparing options, similar mods include Canary and Radium. They cover comparable ground, so the right choice usually comes down to your loader, version, and the rest of your pack.