How many player slots does a Minecraft server need?

A player slot is one available connection to your Minecraft server. The slot limit controls how many players may join at once, but it does not guarantee that the server can run that many players smoothly.

Change the player limit

Stop your server.
Open server.properties.
Set max-players to the maximum number of simultaneous players you want.
Save the file and restart the server.

For example:

max-players=20

What determines actual player capacity?

Performance depends on more than the configured slot count:

available RAM and CPU performance
server software and Minecraft version
plugins, mods, and modpacks
view distance and simulation distance
loaded chunks, entities, farms, and redstone
how actively players explore different areas

Start with a realistic limit, monitor TPS and memory use during busy periods, and optimize or upgrade the server before raising the limit significantly.

What happens when the server is full?

Additional players receive a server-full message. Plugins can provide reserved slots or queues, but their behavior varies by server software and configuration.