In this article, we are going to explain why is your Aternos server lag. If you get this problem, so you are able to read this article until end to find the reasons of Aternos server lag.
DO YOU USE 1.13 / 1.14 OR 1.15?
Since 1.13, Minecraft has a new world format to make the new water changes. Unfortunately, this new world format is not really optimized yet and causes lots of performance issues. They have increased the resources (RAM + CPU) for Vanilla 1.13 and newer servers, but there are still issues that cannot be fixed with more resources. For this case, we recommend you to always use the latest version, it contains the latest optimizations and fixes. The basic performance issue is still present in the newer versions, but hopefully will improve with the newer versions.
Since 1.14.4 Mojang recommends to make a debug report and send it to them when you have performance issue so that they are able to find and fix the causes. You are able to create a debug report with the command: /debug report. You are able to execute that command either in-game or in the console. After that, you are able to find and download the report here: https://aternos.org/files/debug.
DO YOU USE PLUGINS OR MODS?
There are too many or misused mods or plugins can cause server lags. You have to ensure to install a reasonable amount of plugins and do not make too many worlds. Mod features, for example machines or chunk loaders also can cause lags. To identify the issue, you are able to check your log by clicking this link: https://aternos.org/log. Also, it is possible that a single mod contains a bug that causes your server down. For this case, you have to try to remove mod by mod to find out if you are affected by such.
DO YOU USE A MODPACK?
Aternos always try to get the best possible balance between their limited resources and the best performance. Especially for modpacks, this is really hard to achieve. Aternos test the modpacks in their system to make sure that you are at least starting and that basic playing is possible. Because modpacks are always a bit different and the load on their host systems is also always different they cannot guarantee anything here. But, they decided to still offer modpacks on their platform because they want to offer as many options to customize your server as possible and most of the modpacks are nice playable most of the time.
IS YOUR INTERNET STABLE?
Aternos server lag may occur if your internet connection is bad or temporarily overloaded, To test this, you are able to try playing on other servers and check if there are any lags.
It is very unlikely, but possible, that the Aternos host machine is temporarily overloaded. This should only be for a few minutes and rarely happens. In this case, you are able to wait or completely stop and start (not restart) your server.