LagPeek

One command that tells you why your server is lagging.

LagPeek is a tiny, read-only diagnostic tool for Paper servers. Run one command, get an instant snapshot — no setup, no config, no background tasks.

What it shows

Run /lagpeek and you get:

• TPS — 1 / 5 / 15 minute averages, color-coded (green = fine, yellow = struggling, red = lagging)
• Memory — heap used / allocated / max, in MiB
• Chunks — how many chunks are loaded, per world
• Entity hotspots — the top entity types on your server, plus the 10 worst single chunks (entity type, count, and coordinates so you can teleport straight to the problem)

Typical use: server feels laggy → /lagpeek → "oh, 900 zombies in one chunk at ~1240, -380" → go fix it.

Install

1. Drop lagpeek-x.y.z.jar into your plugins/ folder.
2. Restart the server. Done — there is nothing to configure.

Requires Paper 1.21.x (or a fork) and Java 21.

Command & permission

Safe by design

LagPeek only reads server state. It has no event listeners, never edits the world, and runs no repeating tasks — so it cannot conflict with any other plugin. The only network/background activity is a one-time update check on startup (against Modrinth's public API, notify-only) and anonymous bStats usage stats.

Building from source

./gradlew :lagpeek:build

Output: lagpeek/build/libs/lagpeek-<version>.jar