Ever wondered why your Minecraft server feels smooth one minute, then turns into a slideshow the next? The answer usually comes down to ticks and the server’s main thread (often called the mainthread).

In this 2026-friendly guide, you’ll learn what a tick is, what happens during each tick, how lag starts, and how to quickly identify what’s choking your server. Let’s break it down without the headache.

Understand Minecraft server ticks

A Minecraft server runs in a loop, split into small time slices called ticks. Each tick is a “server heartbeat” where the game updates everything that’s happening.

During a tick, the server typically handles tasks like:

• Processing player packets

• Updating entity positions

• Sending world updates to clients

• Running mob AI and pathfinding

• Processing redstone logic

If you want the full deep-dive list, check the reference page: Minecraft Tick.

The goal is 20 ticks per second, which equals 1 tick every 50 ms. That 50 ms budget is the key to understanding performance.

What “normal” tick timing looks like

When your server is healthy, it finishes each tick in under 50 milliseconds. If it completes early, it simply waits (sleeps) until the next tick starts.

Example: if a tick takes 15 ms to process, the server sleeps for about 35 ms. Your gameplay feels responsive, mobs behave normally, and block interactions are instant.

💬 Good to know: A stable server isn’t “working nonstop”. It’s finishing ticks fast enough to keep the 20 TPS rhythm.

Why your server lags when ticks are late

Your server starts lagging when a tick takes longer than 50 ms. Since ticks can’t be processed in parallel, the next tick must wait, and the delay stacks up.

That’s when you’ll see rubberbanding, delayed block breaks, slow mob reactions, and inventory desync. If the server accumulates more than 2000 ms of tick delay, you’ll often get the famous message: "Can't keep up!"

⚠️ Warning: If a tick stalls for more than about 60 seconds, the watchdog usually considers the server “crashed” and may force-stop it.

What the main thread really does

Most Minecraft gameplay logic is single-threaded, meaning it runs on one CPU core: the server’s main thread. Even if your machine has many cores, the mainthread is still the bottleneck for most in-game calculations.

So when people say “my CPU is at 20% but my server lags”, it often means one core is maxed out while the others are chilling. The main thread can’t keep up with the 50 ms tick budget.

📝 Note: Some tasks can be offloaded (network, disk, some async operations), but core gameplay updates are still heavily mainthread-driven.

Common causes of Minecraft server lag

A server lags because it has too much work to finish inside a tick. The classic culprit is too many entities or entity interactions.

Example: for a zombie to attack a player, the server must compute positions, distance, line of sight, pathfinding, target rules, and more. Now multiply that by 500 zombies, every 0.05 seconds, and your mainthread starts sweating.

Farms can be even worse. If you trap 50 chickens in a tight 2x2 space, each chicken constantly collides and pushes others. That can create around 2500 interactions the server must resolve every tick, and that’s before counting hoppers, redstone clocks, or item entities.

💡 Tip: If lag spikes happen when players load farms or mob grinders, you’ve basically found your prime suspect.

Measure performance with TPS

TPS means Ticks Per Second. At 20 TPS, your server processes the expected 20 ticks every second, and gameplay feels “vanilla smooth”. When ticks take too long, TPS drops.

A simplified way to estimate TPS from delay is:

(1000 - delay in ms) / 50 = TPS

For example, if your server accumulates 250 ms of delay per second, your TPS becomes 15. That’s where players start noticing slowdowns, especially in combat and redstone timing.

Identify what’s lagging your server

To find the real cause, you’ll usually want a profiler. The easiest and most common tool is Spark, which can show you exactly what is eating your tick time.

You can follow the MineStrator tutorial here: Analyze your Minecraft server lags.

🚨 Important: Always profile during the lag moment (or right after). A “clean” profile taken when nobody is online won’t reveal the real problem.

Questions frequent

What TPS should I aim for on a Minecraft server?

You should aim for 20 TPS. Small dips are fine, but consistent TPS below 18 usually means players will feel lag.

Why do farms cause so much lag?

Farms often create large amounts of entities, collisions, pathfinding, item drops, and hopper checks. All of that is processed on the main thread, inside the same 50 ms tick budget.

Is “Can’t keep up!” always a CPU issue?

Most of the time it’s mainthread overload (entities, redstone, plugins), but it can also be caused by slow disk I/O, heavy world saves, or misbehaving plugins.

Conclusion

Minecraft server lag is basically a timing problem: if your server can’t finish its ticks within 50 ms, your TPS drops and gameplay suffers. Since most gameplay runs on the main thread, entity-heavy areas and farms are common lag factories.

Want to go from guessing to knowing? Start with profiling using Spark, then optimize what actually consumes tick time. If you need help, check the MineStrator FAQ or contact our Support for guidance.