Server Lags
The first step to take when dealing with lag issues is to determine the nature of the problem—whether it's caused by the client, the server, or the internet service provider.
Ticks per Second
By default, a Minecraft server is designed so that the main game loop executes 20 cycles (called ticks) per second. If this happens, the server has TPS=20. Under heavy load, however, the server may fail to complete calculations on time, causing the number of cycles to drop below 20, which results in server lag.
To check if lag is due to the server, use the /tps command to display the number of ticks per second. If the value is lower than 20, it means the problem lies with the server, which is taking too much time to process calculations.
For Sponge, the command is /sponge tps, and for Forge, it is /forge tps.
Timings - Spigot, Paper, and Sponge
Spigot and Paper come with a very useful diagnostic tool called the /timings command. Bukkit lacks this and many other features, so we encourage switching to the previously mentioned engines.
If you want to figure out why your server is running too slowly, use the /timings on command. Then, for at least 10 minutes, play actively, performing the same actions you usually do. After this period, type /timings paste — you’ll receive a link to a page with detailed (especially for Paper) statistics.
For Sponge, the corresponding commands are /sponge timings on and /sponge timings paste.
You can paste the obtained link on our Discord for advice on optimization.
Spark Profiler - Purpur and Mods
If you’re using a modded server engine or Purpur, or if timings don’t help you identify the cause of server load, you can use what Spark offers. You can download it as a plugin or mod, depending on the engine running on your server. In the case of Purpur, it’s already included, so there’s no need to install it separately. The Spark tool can be accessed via the /spark profiler command.
This method is almost identical to the one mentioned above. To diagnose lag, start by typing /spark profiler start. Then, for at least 10 minutes, play actively, performing the same actions you usually do. After this time, type /spark profiler stop — you’ll receive a link to a page with detailed statistics.