Why Is My Game Server Lagging? How to Find and Fix It

If your game server is lagging, the cause is almost always one of four things: not enough upload speed on the host's internet, not enough RAM, a CPU that cannot keep up on a single core, or a mod, plugin or build that overloads the server. The trick is working out which one. If everyone lags at the same time, it is the server or its connection. If only one player lags, it is usually their connection or their PC.

Quick fix

Try these in order:

Restart the server. Clears memory leaks and stuck processes, and fixes more lag than anything else.
Check whether everyone lags or just one person. One person means their side. Everyone means the server.
Check RAM use. If the server is near its memory limit, it needs a bigger plan or fewer mods.
Check the console for warnings, such as Minecraft's Can't keep up! Is the server overloaded?.
If hosting at home: plug the server into the router with a cable and run an upload speed test.
Remove the last mod or plugin you added and see if the lag stops.

Step 1: work out what kind of lag it is

"Lag" means different things, and each points to a different cause.

What you see	Likely cause
Low frame rate, stutter even when alone	Your own PC or graphics settings, not the server
Everyone rubber bands at the same moment	Server CPU or RAM overloaded, or host upload saturated
One player rubber bands, others fine	That player's connection or Wi-Fi
Lag spikes every few seconds	Server running out of memory, or a save cycle
Gets worse the longer the server runs	Memory filling up or leaking, needs restarts or more RAM
Lag only near one base or farm	Too many entities, machines or redstone in that area
High ping for everyone	Server is far from the players, or a slow home connection

Cause 1: home upload speed

If the server runs on someone's home internet, this is the most common cause. Internet plans are usually sold on download speed, but a server uses upload to send the world to every player. Many cable and DSL plans have a small fraction of their download as upload.

How to check:

Run a speed test on the server PC and look at the upload number.
Run it again while the server is busy. If upload is close to maxed out, that is your lag.
Check for bufferbloat with a bufferbloat test. If ping shoots up when the connection is busy, the router queues traffic badly.
Is anyone else in the house streaming, uploading or on a video call? That shares the same upload.

Fixes:

Use a wired connection for the server. Wi-Fi adds jitter and drops.
Turn on QoS or Smart Queue Management in the router if it has it.
Reduce view or render distance on the server, which sends less data.
Limit the player count.
Move the server off your home connection.

Cause 2: not enough RAM

When a server runs low on memory it stutters, rolls players back, and eventually crashes. How much RAM a game server needs has the full table, but as a rough guide:

Vanilla Minecraft, Terraria and Factorio: 2 to 4 GB.
Valheim: 4 to 8 GB.
Rust, 7 Days to Die, DayZ, Enshrouded, Satisfactory: 8 to 16 GB.
ARK and Palworld: 12 to 24 GB.
Add more for mods and bigger groups.

Signs: java.lang.OutOfMemoryError on Minecraft, lag spikes that come and go, crashes after a few hours, slow chunk loading.

Fixes: restart regularly, remove heavy mods, trim old or unused areas of the world, or move to a bigger plan. On a home server, make sure the server has memory assigned (for Minecraft, the -Xmx flag) and that your own game is not using it all.

Cause 3: CPU, especially single core speed

Most game servers do their main simulation on one thread. That means a fast single core matters more than many cores. A server can lag with plenty of free RAM if one core is maxed out.

Games where this bites hardest:

Minecraft: redstone machines, huge mob farms, and many loaded chunks.
Factorio: megabases. Watch UPS (updates per second): below 60 means the server cannot keep up.
Satisfactory: very large late game factories.
Rust and ARK: many players and structures on a big map.

How to check on Minecraft: Paper ships with spark. Run /spark tps to see ticks per second (20 is perfect) and /spark profiler start, wait a few minutes, then /spark profiler stop to see exactly what is using the time.

Fixes: reduce the load (fewer entities, smaller farms, lower simulation distance), use a performance focused server like Paper on Minecraft, and on a home server close other heavy programs. Running the game and the server on the same PC splits the CPU between both, which is a common cause of lag in co-op hosting.

Cause 4: mods, plugins and builds

One bad plugin or mod can tank a whole server.

Remove the most recently added mod and test.
On Minecraft, the spark profiler shows which plugin or mod uses tick time.
Clear dropped items and excess entities. Many games have commands or plugins for this.
Huge automated builds and farms are a common culprit in every sandbox game.

See how to host a modded game server for version matching and RAM for modpacks.

Cause 5: one player's connection

If only one person lags:

They should use a cable instead of Wi-Fi if they can.
Close downloads, streaming and cloud sync on their side.
Check their ping to the server. Very high ping usually means distance or a poor route.
Restart their router.

The server cannot fix a bad connection on the player's end.

Cause 6: distance to the server

Every server has a physical location, and ping rises with distance. If most of your group lives in one region, the server should be close to them. If players are spread across continents, someone will always have higher ping.

When lag means it is time to move the server

If the server runs on a home PC and you keep hitting upload limits, a PC that also runs your game, or a machine without enough RAM, a hosted server removes those limits. It runs on dedicated hardware in a data center with its own connection, RAM reserved for your server alone, and nothing shared with your household.

On GamezServers, plans are sized by RAM and you can move to a bigger plan any time in Settings, with the new memory applied after a restart. The live console shows warnings as they happen, and the file manager lets you tune configs like view distance. Split the cost with Split with friends at checkout to keep a bigger plan affordable: a 19.99 USD 8 GB server split 4 ways is about 6.00 USD each.

FAQ

Why does my server lag when nobody is doing anything?

Usually memory filling up over time, a heavy farm or machine running in loaded chunks, or a mod doing work in the background. Restart it, then use a profiler or remove recent mods.

Is it the server or my internet?

If everyone lags at the same moment, it is the server or the host's internet. If only you lag, it is your connection or PC.

Does more RAM fix server lag?

Only when the lag is caused by low memory. If RAM use is well below the limit, the cause is CPU, network or a specific mod or build.

Why does my co-op world lag for friends but not for me?

The host's PC runs the game and the server at once, and the host's upload speed limits everyone else. Friends feel it while the host does not. See dedicated server vs peer to peer.

Skip the home internet bottleneck

If upload speed or a busy PC is the problem, a hosted server fixes it. Pick your game on the games page, and see the control panel docs for changing plans later.