Lag after adding a plugin, mod or modpack

The server started lagging after I installed something.

The new plugin or mod is the likely cause: confirm by removing it, then configure it or find an alternative.

Before you start: A backup, and a note of what you added and when.

Step by step

1. Take a backup in the Backups tab so you can undo any test.
2. Remove the most recently added plugin/mod (move its jar out of plugins/ or mods/) and restart.
3. If lag stops, it was that one: check its config for performance options (update intervals, render settings).
4. Map plugins (Dynmap/BlueMap): render at quiet times and lower render threads.
5. Use spark to confirm which plugin uses the most time.
6. Update everything: an outdated plugin on a new Minecraft version often misbehaves.

Check it worked: TPS returns to 20 with only the plugins you need.

Why it happens: Some plugins (maps, anti-cheat, holograms) or heavy mods do a lot of work every tick.

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

• Find out why your server lags
• 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