Find out why your server lags

My server lags. Where do I even start?

Measure first: check TPS, MSPT, memory and CPU, then use a profiler (spark) to see exactly what is slow.

Before you start: A Paper, Purpur or Fabric server (for /tps and spark), and a laggy moment to measure.

Step by step

1. In game or console, run tps (Paper/Purpur). 20 is perfect; under 18 players feel lag.
2. Run mspt: under 50 ms per tick is healthy; above 50 means the server cannot keep up.
3. Open Statistics in the panel: memory near 100% points to RAM; CPU at the plan limit points to CPU.
4. Install spark from the Plugins tab (or the Fabric mod) and run spark profiler start, wait 2 to 5 minutes while it lags, then spark profiler stop.
5. Open the link spark prints. Expand the heaviest entries: entity ticking, a specific plugin, chunk generation or redstone will stand out.
6. Fix the biggest item using the matching guide here (entities, farms, view distance, pre-generation, a plugin), then measure again.
7. If only one player lags and TPS stays 20, it is their connection, not the server.

Check it worked: TPS stays at 20 and MSPT under 50 during your busy time.

Why it happens: Lag is either server lag (low TPS: everyone rubber-bands) or network lag (high ping: one player), and each has different fixes.

If spark shows nothing heavy but TPS is still low, send support the spark link.

More guides on RAM, CPU, performance, and lag:

• Out of memory errors
• RAM always shows high in the panel
• High CPU usage
• Too many entities, mob farms and item build-ups
• Redstone and hopper lag
• View distance and simulation distance