Guide for version 1.16.4
Based on this guide and other sources (all of them are linked throughout the guide when relevant).
To begin I'd like to mention that this is not some sort of "magical cure". There are no guides that will tell you exactly what to do for your server. This is meant to set you in the right direction of finding your server's "sweet spot".
Choice of server jar can make huge difference in performance and api possibilities. There are currently multiple viable popular server jars, but there are also a few that you should stay away from for various reasons.
My recommendation is:- Paper - Most popular server software on latest minecraft version
- Tuinity - Paper fork improving performance with little to no consequences
- Purpur - Tuinity fork that gives you way more configurability and extra features
- Yatopia - "The combined power of Paper forks for maximum instability and unmaintainablity!" - Messy, tossed salad of people that haven't even really understood the patch system and destroys functionality of some of these forks. - KennyTV's list of shame.
- Any paid server jar that claims async anything
Map pregeneration is one of the most important steps to have lag-free server. In modern versions chunk generation is extremely slow and even servers on best hardware can grind into a halt. You can use plugin such as chunky to pregenerate the world. Remember to also set up a world border so your players don't generate new chunks while the server is open to the public! Pregeneration of the map can take hours (it depends on a radius you set in the pregen plugin).
It's key to remember that overworld, nether and the end have separate world borders and you have to set it up for each world. Remember that nether dimension is usually 8x smaller than overworld, because if you set worldborder wrong your players might end up outside of world border!
default: 256optimized: Standalone(512) BungeeCord(-1)
explanation:
This option caps the size of a packet before the server attempts to compress it. Setting it higher can save some resources at the cost of bandwidth, setting it to -1 disables it. If your server is in a network with the proxy on localhost or the same datacenter (<2 ms ping), disabling this (-1) will be beneficial.
default: monsters:70, animals:10, water-animals:15, ambient:15
optimized: monsters:45, animals:8, water-animals:3, ambient:1
explanation:
Lower values mean less mobs. Less mobs is less lag in general, but you want to balance it with player quality of life, finding mobs in the world is big part of gameplay. More detailed explanation of how limits are calculated can be found in this pdf. default: 600
optimized: 400
explanation:
This decides how often vacant chunks are unloaded. Ticking fewer chunks means less TPS consumption. default: 1
optimized: 4
explanation:
This sets how often (in ticks) the server attempts to spawn a monster. Slighty increasing the time between spawns should not impact spawn rates.
default: tile:50, entity:50
optimized: tile:1000, entity:1000
explanation:
Setting those to optimized values disables this feature. You can read why it should be disabled here. default: default
optimized: 3
explanation:
Actual view distance should be set low due to the fact that less chunks will be ticked and paper's no-tick-view-distance lets you send more chunks to player that are actually ticked. default: 8
optimized: 2
explanation:
This usually should be 1 less than view-distance. You can experiment with other values when changing bukkit mob caps. default: animals:32, monsters:32, raiders: 48, misc:16
optimized: animals:16, monsters:24, raiders: 48, misc:8
explanation:
Entities past this range will be ticked less often. Avoid setting this too low or you might break mob behavior (mob aggro, raids, etc). default: true
optimized: false
explanation:
Enabling this prevents the server from ticking villagers outside the activation range. Villager tasks in 1.14+ are very heavy. default: item:2.5, exp:3.0
optimized: item:3.0, exp:6.0
explanation:
This will decide the distance between the items to be merged, reducing the amount of items ticking on the ground. Merging will lead to the illusion of items disappearing as they merge together. A minor annoyance. default: false
optimized: true
explanation:
When enabled, mobs from spawners will not have AI (will not swim/attack/move). This is big TPS savings on servers with mob farms, but also messes with their behavior.
Most of the settings in this file can be configured per-world. See this pdf for details. default: 24
optimized: 8
explanation:
Slows down incremental world saving spreading the task over time even more for better average performance. You might want to set this higher with more than 20-30 players, because if incremental save can't finish in time bukkit will automatically save leftover chunks at once and begin the process again. default: false
optimized: true
explanation:
Faster explosion alghoritm with no impact on gameplay. default: 8
optimized: 2
explanation:
Less collisions calculation per entity. default: 1
optimized: 4
explanation:
Time in ticks before server tries to spread grass/mycelium. No gameplay impact in most cases. default: soft: 32, hard: 128
optimized: soft: 28, hard: 48
explanation:
Lower ranges clear background mobs and allow more to be spawned in areas with player traffic. This further reduces the gameplay impact of reduced spawning (bukkit.yml). Values adjusted for view-distance: 3. default: false
optimized: true
explanation:
This will significantly reduce hopper lag by preventing InventoryMoveItemEvent being called for EVERY slot in a container. Do not enable if you use plugins that listen to this event! default: -1
optimized: 20
explanation:
Makes arrows shot by mobs disappear after 1 second after hitting. default: -1
optimized: 20
explanation:
Makes arrows shot by players in creative disappear after 1 second after hitting. default: false
optimized: true
explanation:
Prevents players from entering an unloaded chunk (due to lag), which causes more lag. The true setting will set them back to a safe location instead. default: false
optimized: true
explanation:
Alternative, faster redstone system. Reduces redundant redstone updates by nearly 95%. default: false
optimized: true
explanation:
This option lets you despawn selected items faster than default despawn rate. You can add things like cobblestone, netherrack etc. to the list and make them despawn after ~20 seconds (400 ticks). default: true
optimized: false
explanation:
Generating treasure maps is extremely expensive and can hang a server if the structure it's trying to locate is really far away. default: -1
optimized: 8
explanation:
This allows players to see further without ticking as many chunks as regular view-distance would. Although it's not really heavy on the server keep in mind that sending more chunks will affect bandwidth. default: false
optimized: true
explanation:
Hides ores from x-rayers. For detailed configuration of this feature check out Stonar96's recommended settings. Paper and its forks in upcoming version 1.17 will require Java 11 (LTS) or higher. Good resolution 2021 to finally update your version of Java!(or at least inform your host so they can handle the migration). JVM can be configured to reduce lag spikes caused by big garbage collector tasks. You can find startup flags optimized for minecraft servers here.
Absolutely unnecessary, can be replaced with spigot configuration (see merge radius and alt-item-despawn-rate) and frankly, they're less configurable than basic server configs. The fact that they usually use more resources to scan and remove items than that items if they would be left alone doesn't help either.
It's really hard to justify using one. Stacking naturally spawned entities causes more lag than not stacking them at all due to server constantly trying to spawn more mobs. Only "acceptable" use case is spawner mobs on servers with large amount of spawners.
Paper offers a `/mspt` command that will tell you how much time server took to calculate recent ticks. If the first and second value you see are lower than 50, then congratulations! Your server is not lagging! If third value is over 50 it means there was at least 1 tick that took longer, that's completely normal and happens from time to time, don't panic.
Great way to see what might be going on when your server is lagging are timings. Timings is a tool that lets you see exactly what tasks are taking the longest. It's the most basic troubleshooting tool and if you ask for help regarding lag you will most likely be asked for your timings.
To get timings of your server you just need to execute `/timings paste` command and click the link you're provided with. You can share this link with other people to let them help you. It's also easy to misread if you don't know what you're doing. There is a detailed video tutorial by Aikar on how to read them.
Spark is a plugin that allows you to profile your servers CPU and memory usage. You can read on how to use it on its wiki.