How to make a SkyFactory 4 server

SkyFactory 4 is the reference skyblock: 13.9 million downloads on CurseForge, a prestige system, and over thirty world types to choose from. You start on one tree and one dirt block, in the middle of the void, and build everything from there.

It's also the pack where the biggest hosting mistake has nothing to do with RAM.

The skyblock trap: the world type

A skyblock pack doesn't just add mods: it changes how the world is generated. The void is the starting set, and it's what gives the whole progression its point.

On a server, that means one thing: if the world is generated with the default type, you get a normal Minecraft with SkyFactory's mods on top. It boots, it runs, nobody sees an error — and the pack is pointless. It's the costliest silent failure of the genre, because you only notice on connecting.

Two practical consequences:

• the world type is chosen at generation, once. Once the map exists, changing the setting changes nothing: the void can't be retrofitted;
• the thirty-odd world types are a permanent decision for that run. Make it with your group before launching, not after.

To try a different type you don't modify the existing world: you create a second server. Server off = €0, so keeping two runs in reserve costs nothing.

What SkyFactory 4 does differently

Two mechanics set this edition apart, and they matter for a group:

• Sky Orchards replace sieving. You grow resources on trees instead of sieving sand for hours. Concretely: less time spent on the same repetitive action, so shorter, denser sessions;
• prestige. Progression doesn't live only in the world: it also accumulates at the player level, and is spent to unlock things. In a group that deserves a conversation — someone who plays twice as much advances twice as fast on that axis.

The pack also leaves room for choice rather than imposing a quest chain: progression runs through advancements. On a server, that means there's no imposed common thread — comfortable, but it requires the group to set its own goal.

Version and Java

SkyFactory 4 targets Minecraft 1.12.2 on the Forge loader — a generation of Minecraft older than most modern packs.

The Java version follows the Minecraft version. The Minecraft Wiki asks for Java 17 from 1.18 and Java 21 from 1.20.5, and "a Java runtime (JRE), version 8 or higher" for earlier versions like this one. If you're self-hosting, that's the first obstacle: a Java picked at random won't start a pack of this generation.

Here, the loader and the Java version come from the pack: nothing to choose.

RAM: what the server actually gets

CurseForge states no official memory figure for SkyFactory 4. The tier below is what we recommend for this pack, not a recommendation from its authors.

What you do need to know is that the number that matters isn't the machine's but the JVM heap (-Xmx), necessarily smaller: the operating system, Docker and Java's off-heap memory live beside it. Here, the heap is the smaller of "RAM − 2 GB" and "75% of RAM":

Take the 16 GB tier. The creation screen warns you if you go below, because it compares heaps, not machine sizes.

CPU, as the factory grows

A skyblock starts tiny and ends up a factory. Resource trees, machines, conveyors, automation: all of it is simulated twenty times a second.

The symptom is distinct from a memory one. A server that falls over is short of heap. A server that drags — slow machines, blocks reacting late — is short of processor. In that second case RAM changes nothing: the dedicated CPU level is what to aim for.

And as on every pack, simulation distance (3 to 32, default 10) is the free thing to try first.

The first boot, and your backups

Expect 15 to 25 minutes on first boot: downloading the pack, resolving mods, writing configuration, then generating the world. Don't kill it thinking it failed — that's the most common phantom failure on big packs. Later boots are quick.

The world is then archived before every shutdown, with a save-all flush immediately before, and restored on the next boot. An automatic backup runs every 30 minutes while you play, of which the last 5 are kept. Storage is free, server off included.

On a skyblock, that backup has particular value: an island represents dozens of hours of patient automation, and it doesn't get rebuilt from memory.

Create your Minecraft server and pick SkyFactory 4 from the modpack list. Your first session is free.