How to Fix a MineColonies Server That Keeps Crashing
MineColonies crashes are usually one of a handful of known causes — too little RAM for continuous colony simulation, a NeoForge version mismatch, or a sub-mod version conflict. See the MineColonies pack page page for boot-tested RAM numbers.
Too little RAM for colony simulation
MineColonies runs continuous AI pathfinding and work-order logic for every colonist across every active colony; the pack's own recommended floor is 6 GB, and undersizing causes freezes that present as a crash. Fix: run at least 6 GB, more as colonies and colonists grow.
Pathfinding deadlock on a malformed colony layout
A building placed with an unreachable work area or blocked path can lock a colonist's AI in a loop that eventually throws a StackOverflowError. Fix: check the crash log for a pathfinding-related class name, then inspect or rebuild the referenced building's access path.
NeoForge version mismatch
MineColonies targets a specific NeoForge build for 1.21.1; a newer or older loader than the one the pack specifies throws NoSuchMethodError on startup. Fix: match NeoForge to the exact version pinned by the modpack, not just 'the latest 1.21.1 build.'
Structurize or BlockUI dependency conflict
MineColonies depends on specific versions of its own sub-mods — Structurize, BlockUI, Domum Ornamentum. Mismatched versions between them is a very common crash source after a manual update. Fix: update all MineColonies-family mods together, from the same release, never individually.
Corrupted colony data after an ungraceful shutdown
Colony state is written continuously; a hard kill mid-write can corrupt a colony's save data, crashing on world load. Fix: restore from backup; always stop gracefully.
Out-of-memory during large building generation
Placing or upgrading a big structure generates and places many blocks in a short window, spiking memory. On a server already near its RAM ceiling this throws OutOfMemoryError. Fix: add RAM headroom proportional to your largest colony's building size, not just player count.
FAQ
What's the minimum RAM for MineColonies?+
Does MineColonies need an exact NeoForge version?+
Why does one specific colony cause crashes while others don't?+
Host MineColonies with the right NeoForge build pinned
CoalHost installs MineColonies with every dependency version matched exactly, so a manual update mismatch never happens.
Deploy MineColonies now →