Sky Factory 4 is one of the most enduring skyblock modpacks, combining automation mods like Applied Energistics 2, Mekanism, and Refined Storage with the classic "start on a floating island" format. Here is what you need to host it well.
What makes Sky Factory 4 different to host
Unlike combat-focused modpacks, Sky Factory 4's resource cost comes from automation, not entity spawning. Large factories full of machines, item transport pipes, and processing chains can generate heavy tick lag even with few players online, since the server has to process thousands of block updates and item movements constantly.
Version, Java and RAM
The last Sky Factory 4 release is 4.2.4 from December 2021. It runs on Minecraft 1.12.2 with Forge 14.23.5.2860 and needs Java 8, not the Java 17 or 21 that newer packs use.
The official server files set a maximum Java heap of 4096M. Java needs some memory on top of the heap, so give the server more than 4GB: 6GB is a comfortable start, and if you raise the heap later, move to a bigger plan with it. The pack does not publish RAM figures per player count. What drives memory in practice is the automation your players build, since late-game worlds with several large factories keep far more machines and items active than a fresh island.
Setup steps
- Download the Sky Factory 4 server files from CurseForge
- Install Forge 14.23.5.2860 for Minecraft 1.12.2, the build the pack uses
- Run the server on Java 8
- Check the heap setting in the server files (4096M by default) and raise it only if the plan has the RAM for it
- Configure server.properties, then start the server and confirm no missing dependencies
Performance tips
- Use a server-side lag-checking tool like Spark to identify which chunk or machine type is causing tick lag
- Cap machine processing speeds in configs if a specific mod (like item pipes) is causing spikes
- Encourage players to keep large factories spread across multiple islands rather than stacking everything on one chunk
- Pre-generate the spawn area, even though Sky Factory 4 worlds are mostly void, spawn chunk loading still matters for performance
Choosing a host
Since Sky Factory 4's demands scale with automation rather than player count alone, plan for growth. Starting on a mid-tier plan and upgrading as factories expand is usually more cost-effective than overbuying RAM on day one. On Space-Node's Minecraft plans, MC Lapis (6GB DDR4) runs the pack's own 4096M heap with room for Java, and MC Diamond (8GB DDR4) lets you raise the heap once builds scale up. Starting a new world? SkyFactory 5 runs on Minecraft 1.20.1 and Java 17; see our SkyFactory 5 server hosting page.
For more modpack hosting comparisons, see our best ATLauncher modpacks guide.