What the mod does
Very Many Players, also called VMP, targets performance bottlenecks on Fabric servers that host crowded worlds. Ishland created it to help hardware keep up when lots of people log in at the same time. The mod focuses on server-side efficiency without altering vanilla game behavior or mechanics.
It is required on the server side, while installation on the game client remains optional. The project is under the MIT License.
Server logic and caching
VMP alters several internal server systems to reduce overhead. It uses area maps to speed up player lookups and nearby packet distribution. Area maps also handle entity tracking.
Caches handle repeat lookups across the game. The mod caches entity trackers, fluid states, ingredient matching, and biome lookups. It also applies caches and specific tweaks to natural spawning logic.
Entity collision loops receive dedicated iteration adjustments. For chunk tickets, VMP integrates the ticket propagator logic from Paper's MCUtil library under an MIT patch. Player logins trigger asynchronous initial chunk loading instead of stalling the server tick. Commands run asynchronously when sent directly by players.
Networking and connection handling
Network traffic often clogs large servers. VMP introduces a custom chunk sending system with optional packet rate limiting. Server administrators get packet-level render distance controls for individual players.
TCP connections adopt packet priority rules derived from raknetify to increase responsiveness. So this networking priority works best when you run the server without reverse proxies like Velocity or SSH port forwarding. For server stability, the mod splits event loops to counter specific bot attacks. Logging operations move off the main thread through AsyncAppender.
On the client side, the mod swaps GLFW time calls over JNI for Java's built-in time source.
Setup and compatibility
VMP requires Java 17 or later to build and run. So it targets the Fabric loader.
Supported Minecraft versions listed in the project data are 26.3, 26.2, 26.2-rc-2, 26.1.2, 26.1.1, 26.1, 26.1-rc-3, 26.1-rc-2, and 26.1-rc-1. Honestly, the developers note that combining VMP with Lithium is recommended for top performance.
The project remains in early development, so bugs can happen. Issues belong on the official issue tracker.
