How Mob Spawners Affect Server Performance

Direct answer

For cage spawners, measure how many spawners are active and how quickly spawned mobs leave their activation area. Spawner tick checks and mob AI are separate costs.

How to check it

1. Count active spawner blocks and identify whether the player is within their activation distance. Compare MSPT with players near and away from the area.
2. Profile with /spark profiler start --timeout 300 and inspect entity work versus block-entity/spawner work. Record the number of mobs left alive near each cage.
3. Inspect farm design for overcrowding near the spawn block; a clogged mob pile can prevent output while still consuming AI work.

What to change

1. Move mobs out of the cage area promptly and prevent unbounded accumulation while maintaining safe gameplay.
2. Paper world config includes tick-rates.mob-spawner. It controls spawner check frequency and -1 disables spawners; changing it alters spawn rates, so test on a copy.
3. nerf-spawner-mobs in spigot.yml disables most AI for mobs from spawners. It may break transport or combat behavior. Treat it as a gameplay change, not a universal recommendation.

Software and version notes

Verify the result

Compare spawns per minute, player experience, active entity counts and MSPT, and ensure the spawner still produces the desired mobs.

References

• PaperMC Spigot configuration
• PaperMC world configuration
• PaperMC profiling guide