When running an online world in Minecraft, it is common for latency issues or "lag" to occur. When lag arrives, it can create a frustrating experience as actions and activity in the world are delayed compared to a single-player world.
It's a complicated question, as online servers and worlds can be influenced by many things that can cause many problems. However, not all of these factors are equal, and some issues cause much more lag than others.
When troubleshooting a world or a server full of worlds, it's best to begin with, the most common and glaring sources of lag or other network connectivity issues. These causes won't be the reason for every Minecraft world's lag, but there are a few things players can check on their end to be sure.
Minecraft could be lagging for a number of reasons, but these are the most common
5) Player count
Depending on what hardware you're running your online Minecraft world on, there's a certain amount of players you should expect to have. If you allow more player connections than your hardware can handle, lag will almost certainly appear.
To amend this problem, it's wise to keep a maximum cap on how many players can join your world, upgrade your network infrastructure via RAM upgrades, or seek a professional hosting service.
Don't expect to run a Minecraft world with hundreds or thousands of players without a high-quality machine or a professional host.
4) High entity count
Much like the presence of players, entities like mobs can induce plenty of lag on their own. Considering a world/server must simulate the activity of every entity currently loaded in a world's chunks, it takes quite a bit of RAM once the entity count starts to increase.
If you're operating a large world with several entities simulating at once, lag may be the least of your issues, as a vast entity count can even cause crashes.
There are ways to set a limit on entities in your world, and there are also helpful Minecraft plugins and mods that will "prune" entities away from players to reduce CPU load.
3) Distance from your server
When you're hosting a Minecraft world/server, location is critical. Depending on how far away a player's machine is from the server, it takes longer to communicate back and forth. This is typically known across gaming as "ping" and applies to Minecraft, like many other games.
While there are ways to mitigate ping, sometimes a player's location in a particular region can lead to in-game lag. There are undoubtedly various ways to address ping in-game. Sometimes a server's hosting location is too far away for players in certain parts of the world.
2) Console spam
Minecraft's command console is incredibly helpful when it comes to keeping a world or server of worlds running. Sometimes command blocks are needed to assist players with certain tasks, and plugins can occasionally output into the console. If the console is flooded with input from command blocks, plugins, or even chat spam, it can cause problematic lag issues.
Like handling mobs and players, your world has to handle the in-game console differently. If a command block executes commands repetitively and quickly or a plugin displays clockwork errors, connection problems can ensue.
1) Plugins and mods
If you've been modding or adding plugins to your Minecraft world/server, checking in on them is almost certainly the first thing you want to do when you're having lag issues. Some additions to the game can be hefty on CPU and RAM usage, and this is one of the biggest creators of lag due to the world attempting to free up resources.
There's also the matter of compatibility. Many mods and plugins don't work well together, leading to errors causing in-game hang-ups and dumping errors into the command console. This leads to plenty of headaches for an administrator. The best fix is to upgrade your Minecraft server's RAM capacity or remove/disable specific non-compatible mods. At the very least, figure out what plugins or mods are having issues and seek to resolve them specifically.