How to Fix a Medieval MC [FORGE] Server That Keeps Crashing
Medieval MC ships as multiple separate editions — FORGE, MMC2/MMC3 on Fabric, MMC4, MMC5 on NeoForge — and they do not interoperate. Most reported 'crashes' turn out to be a player on the wrong edition trying to join a FORGE server, not an actual bug.
See the Medieval MC [FORGE] pack page for sizing before you chase anything else.
1. The wrong edition entirely
Medieval MC isn't one pack with versions — it's several separate, incompatible editions published side by side: FORGE, MMC2 [Fabric], MMC3 [Fabric], MMC4, and MMC5 [NeoForge]. A player seeing a mod-list mismatch has almost always installed a different edition, often by grabbing an old Modrinth mirror or confusing MMC5 for the FORGE edition.
Fix: have every player reinstall from the exact Medieval MC [FORGE] CurseForge page and confirm the loader (Forge, not Fabric or NeoForge) matches what the server runs.
2. RAM — server and client both
This is a resource-intensive pack on both ends. If the server has plenty of RAM but a specific player keeps crashing, their own client needs at least 6 GB too — a client-side out-of-memory crash can look like a server problem but has nothing the server operator can fix.
3. Wrong Java version
Run the exact Java version the pack specifies. An older or newer JDK than intended is a quiet, easy-to-miss cause of startup failures that otherwise look like a mod conflict.
FAQ
Why can't my friend connect to my Medieval MC [FORGE] server?+
Medieval MC publishes several separate editions — FORGE, MMC2 [Fabric], MMC3 [Fabric], MMC4, MMC5 [NeoForge] — and they can't join each other. A 'mod mismatch' error almost always means your friend installed a different edition (often MMC5 or an old Modrinth copy) than the FORGE server you're running. Reinstall from the exact CurseForge page for Medieval MC [FORGE] and match versions.
How much RAM does Medieval MC [FORGE] need?+
It's a resource-intensive pack — give the server itself a solid allocation, and remind players their own client needs at least 6 GB too, since a client running out of memory produces a crash that looks server-side but isn't fixable from the server end.
What if I'm still stuck after checking the edition and RAM?+
Confirm you're on the Java version the modpack specifies, then open a support ticket with your latest.log and crash report attached — the Medieval MC team asks for exactly this when a crash doesn't match the common patterns.
Host Medieval MC [FORGE] on the matching edition every time
CoalHost installs the exact Medieval MC edition and loader you pick — no mixing FORGE with an MMC5 client by accident.
View Medieval MC Hosting →