Profiling Lag with spark
spark is a performance profiler for Minecraft servers. Instead of guessing what's causing lag, spark measures it, telling you which plugins, mods, or tasks are consuming the most time and memory.
spark is available for Paper, Spigot, Fabric, and Forge. Some server software (like Paper) even bundles it. Install it like any other plugin or mod and restart.
Checking Server Health
For a quick overview, these commands report live stats:
| Command | What it shows |
|---|---|
/spark tps | Current TPS and CPU usage. |
/spark health | A summary of TPS, tick durations, and memory usage. |
/spark heapsummary | A breakdown of what's using memory. |
Running a Profiler Report
To find what's actually eating your tick time:
- Start the profiler while the lag is happening:
/spark profiler start - Let it run for a minute or two of normal (or laggy) activity.
- Stop it to generate the report:
/spark profiler stop
spark uploads the results and gives you a link to an interactive web viewer. There you can drill down into exactly which code paths, and which plugins or mods, are taking the most time.
When asking for support with lag, share your spark report link rather than describing the problem. It gives staff everything they need to diagnose the cause quickly.