// modpack server guide
Medieval MC (MMC4) server hosting & setup guide
An MMC4 server needs Java 17 and about 9–11 GB of RAM for up to 8 players.
Version 1.20 | Medieval Fantasy RPG Adventure & Exploration Modpack everyone wants!
Summary from Medieval MC (MMC4) on Modrinth.
Medieval MC (MMC4) is a Forge modpack for Minecraft 1.20.1 with 312 mods. We'd pick our Heavy plan (12 GB) for it.
Quick facts
| Loader | Forge |
|---|---|
| Minecraft versions | 1.20.1 |
| Java needed | Java 17 for Minecraft 1.20.1 Java version chart. |
| Mods | 312 modsCounted from the pack's file list on Modrinth. None are marked client-only. |
| RAM | About 8–9 GB for 1–3 playersBy player count. |
| Downloads | 192,500 on Modrinth |
| Last updated | February 8, 2025 (version v30) |
| First published | July 19, 2023 on Modrinth |
| Server support | Required: the pack has mods that must run on the server. |
| Server pack | SERVER_ONLY_MMC4_v39.zipOfficial server pack on CurseForge, for Medieval MC [FORGE] 1.20.1 v39. Checked October 5, 2026. |
| Modrinth tags | adventure, combat, magic, challenging, lightweight, optimization |
MMC4 server files
Yes, on CurseForge. Modrinth has no separate server pack for MMC4, but the authors publish one on CurseForge: SERVER_ONLY_MMC4_v39.zip, for Medieval MC [FORGE] 1.20.1 v39 (February 26, 2026).
That's not the version Modrinth has (v30). A server and its players must run the same pack version, so either install the client pack from CurseForge too, or build the server from the Modrinth pack instead.
How much RAM does an MMC4 server need?
| Players online | RAM | DSN plan |
|---|---|---|
| 1–3 players | About 8–9 GB | Heavy (12 GB)Premium (8 GB) can do if players stay close. |
| 4–8 players | About 9–11 GB | Heavy (12 GB) |
| 9–15 players | About 10.5–13.5 GB | Heavy (12 GB) if players stay closeMore than 12 GB if they spread out. |
Estimated from 312 mods on the server with our RAM calculator, not measured: low end if players stay together, high end if they spread out.
With 9–15 players spread across the map, MMC4 can need more than 12 GB, our biggest plan. A lower view distance and a pre-generated world help it fit; past that, a host with bigger plans is the better choice.
Set Java's heap (-Xmx) 10–15% under the RAM you have, about -Xmx10500M on 12 GB. Forge 1.20.1 reads it from user_jvm_args.txt: uncomment the -Xmx line. RAM guide.
MMC4 server requirements
| Java | Java 17 |
|---|---|
| Loader | Forge for Minecraft 1.20.1 |
| CPU | Fast single-core speed (one main thread). With 312 mods, the first start takes minutes. |
| RAM | About 8–13.5 GB for 1–15 players (table above) |
| Disk | The server files, a growing world and backups |
| Network | TCP port 25565 open to players |
Recommended plan
Our pick for MMC4
Heavy
12 GB RAM · planned launch price $42/month
At about 312 Forge mods this is a heavy pack, and 12 GB keeps it clear of out-of-memory crashes.
Ordering is closed until we relaunch. We aren't taking orders or payments while we move to new hardware. Join the launch list and we'll email you when Heavy servers open.
Heavy is our biggest plan. Not sure? Email hello@dsnservers.com.
Planned launch price in USD, billed monthly once ordering opens, with a 7-day refund window.
How to make an MMC4 server on your own PC
What's specific to MMC4, step by step. The full walkthrough for any pack: how to make a modded Minecraft server.
- Install Java 17.
Check with
java -version. Java version chart. - Get the server files.
Download the official server pack,
SERVER_ONLY_MMC4_v39.zip, from CurseForge and unzip it into an empty folder. Make sure your players install the same pack version. - Start it and accept the EULA.
Run the start script in the server files, or the
run.sh/run.batthe Forge 1.20.1 installer writes, then seteula=trueineula.txtif you accept Mojang's EULA (EULA step). With 312 mods, the first start takes minutes. - Set the RAM with
-Xmx, sized from the table above. - Let friends connect: forward TCP 25565, or use a tunnel or host behind CGNAT (can't connect?).
Or run MMC4 on DSN
Once we relaunch (join the launch list), on DSN you'd install MMC4 from the panel's Modrinth modpack installer (version v30), pick Java 17 on the Startup tab and accept the EULA in the console. No port forwarding.
How to play MMC4 with friends
Each player installs MMC4 version v30 with the Modrinth App or Prism Launcher, the same version as the server, and adds the server's address under Multiplayer.
Different versions of MMC4 on the server and a client show up as Mismatched mod channel list or mod rejections. Why friends can't join, timeouts included.
Lag and performance on MMC4
Can't keep up! Is the server overloaded? means ticks take longer than 50 ms; more RAM won't fix that once MMC4 has enough (tick lag guide). For MMC4:
- Measure first: spark's
/spark tpsand profiler work on 1.20.1 and name the mod or machine using the tick time. - Distances:
view-distance=8and a lowersimulation-distanceinserver.properties. - Pre-generate: Chunky for 1.20.1,
/chunky radius 3000then/chunky start, before people explore. - Chunk loaders keep machines running with nobody nearby; in a pack this size, dozens add up.
Common MMC4 crashes
What a Forge 1.20.1 server running MMC4 hits most. For any other error, paste the log into the free crash log analyzer.
- Out of memory. MMC4 (312 mods on the server) needs about 8–9 GB for 1–3 players;
java.lang.OutOfMemoryErrormeans it ran out. Out-of-memory fix. - Wrong Java version. MMC4 on Minecraft 1.20.1 needs Java 17. Started on Java 8, it stops with
UnsupportedClassVersionError: ... class file version 61.0, this version of the Java Runtime only recognizes class file versions up to 52.0. Java version fix. - Client-only mod on the server. The MMC4 pack file marks none of its mods client-only, so this usually means one was copied over from a player's mods folder. Check a mods list with the client-or-server-side checker. Client-only mod fix.
- After adding or updating a mod. Mods you add to MMC4 by hand usually crash it with a missing dependency or a mixin conflict.
- Ticking entity or block entity. The crash report names it and gives its coordinates. Ticking entity fix.
Updates and support
Before moving MMC4 past version v30, back up the world: see updating a modpack server without losing your world.
Bugs in MMC4 itself go to its authors: issue tracker, wiki and Discord. Server problems on DSN: hello@dsnservers.com or Discord.
Packs like MMC4
More: all modpack guides and how to make a modded server.
Run MMC4 on DSN when we relaunch.
Our pick, Heavy: 12 GB, planned at $42/month.
DSN Servers isn't affiliated with Medieval MC (MMC4) or Modrinth. The pack's icon, summary and stats come from Modrinth's public API (checked October 4, 2026).