«The server is lagging» describes two completely different problems with completely different fixes. Five seconds of checking tells you which one you have, and saves you from optimising the wrong machine.
What you are seeing
- Blocks take a moment to break, or reappear after breaking.
- Mobs slide or teleport instead of walking.
- The game looks choppy but everything responds instantly.
Why it happens
TPS is how many times per second the server updates the world; 20 is full speed. FPS is how many frames per second your own computer draws. Low TPS is the server. Low FPS is your computer. They feel different once you know what to look for.
What to do
- Run
tpsin the consolePaper, Spigot and Purpur all answer with the last 1, 5 and 15 minute averages. Anything from 19.5 upwards is healthy. Below 18 the world is genuinely running slow.
- Press F3 in game and read the FPS counter
It is in the top left. If FPS is low but the server reports 20 TPS, the server is fine and the bottleneck is your graphics settings or your machine.
- Match the symptom to the number
Blocks that reappear after breaking, mobs that slide, delayed chest opens — that is low TPS. A choppy picture with instant responses is low FPS.
You know which number is the low one. From here, low TPS points at the server-side articles in this section; low FPS points at your video settings.
High ping is a third thing again: the world updates fine and your frames are fine, but everything you do takes a moment to reach the server. That one shows up as delay, not stutter.