// modpack server guide
Cobblemon Islands server hosting & setup guide
A Cobblemon Islands server needs Java 21 and about 2.5–3.5 GB of RAM for up to 8 players.
Every Pokemon model, Megas, Z-Moves, raids, gyms, dens, and expeditions on one Cobblemon server. Install and the server is already in your multiplayer list.
Summary from Cobblemon Islands on Modrinth.
Cobblemon Islands is a Forge and Fabric modpack for Minecraft 1.21.1 (older versions go back to 1.20.1) with 79 mods, 38 of which run on the server. We'd pick our Standard plan (4 GB) for it.
Quick facts
| Loader | Forge and Fabric |
|---|---|
| Minecraft versions | 1.21.1, 1.20.1 |
| Java needed | Java 21 for Minecraft 1.21.1Older pack versions: Java 17 for 1.20.1. Java version chart. |
| Mods | 38 run on the server79 in the pack. The other 41 are client-only, and the server skips them. |
| RAM | About 2–2.5 GB for 1–3 playersBy player count. |
| Downloads | 194,899 on Modrinth |
| Last updated | September 6, 2026 (version 2.7.4) |
| First published | October 19, 2023 on Modrinth |
| Server support | Supported: it runs on a server, and works in single player too. |
| Server pack | Not published separatelyHow to build the server. |
| Modrinth tags | adventure, quests, challenging, combat, lightweight, optimization |
Cobblemon Islands server files
No. Cobblemon Islands has no separate server pack on Modrinth, so the server is built from the .mrpack: the Forge or Fabric server for Minecraft 1.21.1, plus the pack's overrides folder and the server-side mods its modrinth.index.json lists. A modpack installer does this for you; our guide shows how to make a server for a modpack with no server pack.
How much RAM does a Cobblemon Islands server need?
| Players online | RAM | DSN plan |
|---|---|---|
| 1–3 players | About 2–2.5 GB | Standard (4 GB) |
| 4–8 players | About 2.5–3.5 GB | Standard (4 GB) |
| 9–15 players | About 3–4.5 GB | Premium (8 GB)Standard (4 GB) can do if players stay close. |
Estimated from 38 mods on the server with our RAM calculator, not measured: low end if players stay together, high end if they spread out.
Set Java's heap (-Xmx) 10–15% under the RAM you have, about -Xmx3500M on 4 GB. Forge 1.21.1 reads it from user_jvm_args.txt: uncomment the -Xmx line. RAM guide.
Cobblemon Islands server requirements
| Java | Java 21 |
|---|---|
| Loader | Forge or Fabric for Minecraft 1.21.1 |
| CPU | Fast single-core speed (one main thread). |
| RAM | About 2–4.5 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 Cobblemon Islands
Standard
4 GB RAM · planned launch price $16/month
At about 38 mods this is a light pack, so 4 GB of RAM covers it for a small group.
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 Standard servers open.
More than 8 players, or lots exploring at once? Go up to Premium (8 GB). 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 a Cobblemon Islands server on your own PC
What's specific to Cobblemon Islands, step by step. The full walkthrough for any pack: how to make a modded Minecraft server.
- Install Java 21.
Check with
java -version. Java version chart. - Get the server files.
Build them from the .mrpack, as in server files above.
- Start it and accept the EULA.
Run the start script in the server files, or the
run.sh/run.batthe Forge 1.21.1 installer writes, then seteula=trueineula.txtif you accept Mojang's EULA (EULA step). - 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 Cobblemon Islands on DSN
Once we relaunch (join the launch list), on DSN you'd install Cobblemon Islands from the panel's Modrinth modpack installer (version 2.7.4), pick Java 21 on the Startup tab and accept the EULA in the console. No port forwarding.
How to play Cobblemon Islands with friends
Each player installs Cobblemon Islands version 2.7.4 with the Modrinth App or Prism Launcher, the same version as the server, and adds the server's address under Multiplayer.
Different versions of Cobblemon Islands 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 Cobblemon Islands
Can't keep up! Is the server overloaded? means ticks take longer than 50 ms; more RAM won't fix that once Cobblemon Islands has enough (tick lag guide). For Cobblemon Islands:
- Measure first: spark's
/spark tpsand profiler work on 1.21.1 and name the mod or machine using the tick time. - Distances:
view-distance=8and a lowersimulation-distanceinserver.properties. - Pre-generate: Chunky for 1.21.1,
/chunky radius 3000then/chunky start, before people explore.
Common Cobblemon Islands crashes
What a Forge and Fabric 1.21.1 server running Cobblemon Islands hits most. For any other error, paste the log into the free crash log analyzer.
- Wrong Java version. Cobblemon Islands on Minecraft 1.21.1 needs Java 21. Started on Java 17, it stops with
UnsupportedClassVersionError: ... class file version 65.0, this version of the Java Runtime only recognizes class file versions up to 61.0. Java version fix. - Out of memory. Cobblemon Islands (38 mods on the server) needs about 2–2.5 GB for 1–3 players;
java.lang.OutOfMemoryErrormeans it ran out. Out-of-memory fix. - Client-only mod on the server. Cobblemon Islands includes 41 client-only mods, which a server install skips; copying a player's mods folder brings them back and stops the server. 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 Cobblemon Islands 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 Cobblemon Islands past version 2.7.4, back up the world: see updating a modpack server without losing your world.
Bugs in Cobblemon Islands itself go to its authors: wiki and Discord. Server problems on DSN: hello@dsnservers.com or Discord.
Packs like Cobblemon Islands
More: Cobblemon server hosting, all modpack guides and how to make a modded server.
Run Cobblemon Islands on DSN when we relaunch.
Our pick, Standard: 4 GB, planned at $16/month.
DSN Servers isn't affiliated with Cobblemon Islands or Modrinth. The pack's icon, summary and stats come from Modrinth's public API (checked October 4, 2026).