Pregenerating Your Minecraft World: What to Know Before You Start

Somewhere out there, a player just got an elytra and decided to explore. They’re rocketing across your server at 30+ blocks per second, and your TPS is tanking because the server can’t generate terrain fast enough to keep up. Sound familiar?

Chunk generation is one of the most CPU-intensive things a Minecraft server does. Every time a player enters unexplored territory, your server has to calculate terrain height, place structures, generate caves, spawn entities, and compute lighting - all in real time. On modern versions with deeper worlds and more complex terrain, this hits even harder.

Pregeneration solves this by doing all that work ahead of time, before your players ever log in. It’s one of the highest-impact optimizations you can do for exploration-heavy servers, and it costs nothing but time and planning. The payoff is smoother TPS during gameplay, fewer lag spikes during exploration, and less memory pressure from generation bursts - which means that RAM you’re paying for goes toward running your server, not generating terrain on the fly.

This guide focuses on the strategic decisions: whether you need to pregen, how much, and when. For the step-by-step Chunky commands, we have a detailed walkthrough in our help center.

Why Chunk Generation Hurts So Much

When Minecraft generates a new chunk, it’s not just placing blocks. The server runs through terrain shaping, biome assignment, structure placement (villages, strongholds, mineshafts), ore distribution, cave carving, feature decoration (trees, flowers, grass), entity spawning, and lighting calculations. Each chunk is 16x16 blocks and now extends from Y -64 to Y 320 - that’s a lot of data to compute.

This got noticeably worse after 1.13’s aquatic update changed how terrain generates, and again with 1.18 when world height increased by 50%. The terrain algorithm is more complex, there’s more vertical space to fill, and caves are significantly more elaborate than they used to be.

The real killer is that generation is CPU-bound. You can throw more RAM at a server and it helps with loaded chunks, but generation speed is limited by how fast your processor can run the worldgen code. When a player on an elytra is moving faster than the server can generate, something has to give - and that something is your tick rate.

We see this in support tickets regularly: servers running fine until someone decides to go exploring, then suddenly TPS drops to single digits. The player flying into uncharted territory is generating dozens of chunks per second, and the server just can’t keep up.

Do You Actually Need to Pregen?

Not every server needs pregeneration. If you’re running a small vanilla SMP with five friends who mostly hang out near spawn, the occasional exploration lag probably isn’t worth the setup time. But as your server grows or your modpack gets heavier, the calculus changes.

Here’s a rough guide:

You can probably skip it if:

• Small friend group on vanilla (under 10 players)
• Players mostly stay near spawn
• Exploration happens slowly and infrequently
• You’re okay with occasional lag during adventures

You should strongly consider it if:

• Public server with 15+ players
• Active explorers or players who use elytra frequently
• You want consistent TPS regardless of player activity
• You’re planning to run the server long-term

You almost certainly need it if:

• Running any modded server (especially with custom worldgen)
• Heavy modpacks like All The Mods, Create, or similar
• Using terrain generation mods like Terra or Terralith
• Players have complained about exploration lag

Here’s something we’ve noticed: some server owners on smaller plans use pregeneration specifically to avoid needing an upgrade. If your world is pregenerated, your server isn’t spending resources on chunk generation during gameplay - which means that 4GB plan stretches further than it would otherwise. The RAM and CPU that would go toward generating new chunks can instead go toward running your plugins, mods, and player activity.

Picking the Right World Size

World size scales quadratically. Double the radius and you get four times the area, four times the storage, and roughly four times the generation time. This catches people off guard - a 10k radius world isn’t twice as big as a 5k radius world, it’s four times as big.

The table below uses radius in blocks (what you’d pass to chunky radius or half of what you’d pass to worldborder set). Storage estimates are rough - actual size varies by seed, terrain, and version:

A few notes on this table: these are starting points, not hard rules. Your specific situation matters. A server where everyone builds mega-bases near spawn needs less radius than one where players spread across the map. A modpack with aggressive worldgen might need more headroom.

Because Nether coordinates scale 8:1 with the overworld, you’ll usually want a smaller Nether border and pregen radius. If your overworld border is 5,000 blocks, a Nether radius around 625 keeps portal travel aligned - players won’t be able to use the Nether to bypass your overworld border. That 625 number is only if you want Nether travel to map cleanly to your overworld edge; it’s totally fine to go larger if you want more Nether space for bases or hubs. You can pregen the Nether at whatever radius makes sense for your server.

If you want to estimate storage more precisely, tgb’s World Size Calculator lets you plug in your radius and see estimates for each dimension.

Timing and Logistics

The ideal time to pregen is before your server goes public. No players means Chunky can use all available resources, and you won’t have anyone complaining about lag during the process.

If you’re adding pregeneration to an existing server, pick a maintenance window. Let players know the server will be laggy or offline, and run it during off-hours if possible.

Before you start, make sure you’ve:

• Taken a backup (pregeneration is safe, but backups are always smart)
• Disabled map renderers temporarily (Dynmap, BlueMap, Squaremap)
• Confirmed you have enough free disk space for the world size you’re targeting

A few practical considerations:

Memory management matters. Chunky can use a fair amount of RAM during generation, especially on larger worlds. If your server runs low on memory, it might crash mid-generation. Two things help here: set continue-on-restart: true in Chunky’s config file so it picks up where it left off after a restart, and consider using scheduled restarts (every 20-30 minutes) to clear memory periodically. Our help center article has more details on this.

Remove unnecessary plugins during generation. Anything that hooks into chunk loading or entity spawning adds overhead. If you can temporarily disable map renderers (Dynmap, BlueMap, Squaremap), protection plugins, and similar, generation goes faster.

Don’t have players online. Even if Chunky can technically run with players connected, you’re asking it to share resources that could be going toward generation. Players will experience lag, and generation will be slower. Just don’t.

One tradeoff to keep in mind: larger pregenerated worlds mean larger backups and longer restore times. A 5k radius world backing up in 2 minutes might become a 10k radius world that takes 8+ minutes. If you’re running automated backups, make sure your backup interval accounts for this. It’s not a reason to skip pregeneration, but it’s worth planning for.

Another consideration: pregenerated chunks use the worldgen that existed when you ran Chunky. New content from terrain mods, datapacks, or Minecraft updates only appears in new chunks. To get new worldgen in old areas you’d have to regenerate those chunks (which can delete builds), so most servers leave room to expand instead. This is another reason to start smaller: it’s easier to grow your border than to deal with mixed terrain.

Planning for Future Updates

If you’re running a server you expect to keep for multiple Minecraft versions, think ahead. New versions often add content that only generates in new chunks - 1.20’s cherry groves, 1.21’s trial chambers, and whatever comes next.

Starting with a smaller pregenerated area (say, 5k radius) gives you room to expand when updates drop. When 1.22 comes out with some new biome, you can bump your world border to 8k and run Chunky again. Players get a clear “new content zone” to explore, and you’ve kept your world size manageable in the meantime.

This is also why the quadratic scaling matters. If you pregen 20k on day one because you want “plenty of room,” you’ve now got a massive world file, longer backup times, and nowhere obvious to put new content when it releases.

A Note on Modded Servers

Modded servers benefit the most from pregeneration, but they also present the biggest challenges. Custom worldgen mods like Terra, Terralith, or Oh The Biomes You’ll Go make terrain generation significantly more expensive. Heavy modpacks add entity types, block types, and worldgen features that all need processing.

If you’re running a major modpack, pregen isn’t optional - it’s survival. We see modded servers where exploration lag is so severe that players avoid it entirely. That’s not a fun gameplay experience.

A few modded-specific tips:

Test with a small radius first (1-2k) to see how long generation takes and catch any issues. Some modpacks include their own pregeneration features - check before installing Chunky separately. Heavy packs benefit from starting smaller (3-5k) because expanding later is easier than waiting days for initial generation.

Get It Done Before Launch

Pregeneration is one of those optimizations that feels like extra work until you see the results. Better TPS during gameplay, lower memory pressure, and players who can actually use their elytras without crashing the server - it’s worth the upfront investment.

The key decisions are: do you need it (probably, if you’re reading this), how much (start conservative, expand later), and when (before players if possible).

For the actual Chunky commands and step-by-step process, check out our Chunky guide in the WinterNode help center. It covers installation, world border setup, and all the commands you’ll need.

If You’re Looking for Hosting

We’re obviously biased, but WinterNode exists because we wanted hosting that didn’t nickel-and-dime people. All our Game Servers are priced at $1.99/GB of RAM - we don’t charge extra for CPU usage, storage space, or basic features that other hosts mark up.

If you want to test the waters, we offer a 48-hour free trial on Minecraft servers. No credit card required.

Got questions? Our support team responds to tickets with actual humans, and we’re active on Discord if you prefer chatting there.