How to Fix an RLCraft Server That Keeps Crashing
RLCraft crashes are usually one of a handful of known causes — the wrong Java version, too little RAM for Lycanites Mobs and the progression systems, or a Forge version mismatch. See the RLCraft pack page page for boot-tested RAM numbers.
Running Java 17+ instead of Java 8
RLCraft is built on Forge 1.12.2, which requires Java 8; running it under a newer JVM throws UnsupportedClassVersionError or silently misbehaves with Forge's older class-loading. Fix: pin the server's JAVA_HOME to a Java 8 runtime specifically for RLCraft.
Too little RAM for Lycanites Mobs and progression systems
RLCraft keeps hundreds of entities active via Lycanites Mobs alongside heavy progression and attribute mods; the pack needs a minimum of 8 GB, with 10-12 GB recommended. Fix: run at least 8 GB, more for multiple active players.
Out-of-memory during initial world generation
RLCraft's biome and structure generation is heavier than vanilla; a RAM-tight server can run out of memory during the first chunk-generation wave before anyone even joins. Fix: temporarily raise RAM for the first boot or world-gen pass if borderline.
Corrupted chunk from a Lycanites Mobs entity
A malformed mob entity — from a bad spawn or a mod update mid-session — can crash the server every time that chunk loads. Fix: identify the crash coordinates from the log and delete that region file, or roll back to a backup.
Outdated server pack after an RLCraft update
RLCraft updates its full mod list together; mixing an old server pack with newer client mods, or vice versa, causes immediate mismatch crashes on connect. Fix: always download the matching server pack version for your installed RLCraft client version.
Forge version mismatch
RLCraft pins an exact Forge build for 1.12.2; a different Forge version, even a small patch difference, can throw mod-loading errors. Fix: use the exact Forge version listed on RLCraft's CurseForge page.
FAQ
What Java version does RLCraft need?+
How much RAM does RLCraft need?+
Why does my server crash in the exact same spot every time?+
Host RLCraft with Java 8 locked in by default
CoalHost pins the right JVM and Forge build for RLCraft automatically, so this mismatch never happens.
View RLCraft Hosting →