// modpack server guide
Horizons server hosting & setup guide
A Horizons server needs Java 17 and about 5.5–7 GB of RAM for up to 8 players.
The Horizons Project is a modpack created for rubius. Released so that others can enjoy the same experience as well.
Summary from Horizons on Modrinth.
Horizons is a Fabric modpack for Minecraft 1.20.1 with 164 mods. We'd pick our Premium plan (8 GB) for it.
Quick facts
| Loader | Fabric |
|---|---|
| Minecraft versions | 1.20.1 |
| Java needed | Java 17 for Minecraft 1.20.1 Java version chart. |
| Mods | 164 modsCounted from the pack's file list on Modrinth. None are marked client-only. |
| RAM | About 4.5–5.5 GB for 1–3 playersBy player count. |
| Downloads | 248,678 on Modrinth |
| Last updated | January 21, 2025 (version 1.5) |
| First published | June 17, 2024 on Modrinth |
| Server support | Required: the pack has mods that must run on the server. |
| Server pack | Not published separatelyHow to build the server. |
| Modrinth tags | adventure, challenging, optimization |
Horizons server files
No. Horizons has no separate server pack on Modrinth, so the server is built from the .mrpack: the Fabric server for Minecraft 1.20.1, 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 Horizons server need?
| Players online | RAM | DSN plan |
|---|---|---|
| 1–3 players | About 4.5–5.5 GB | Premium (8 GB) |
| 4–8 players | About 5.5–7 GB | Premium (8 GB) |
| 9–15 players | About 6.5–9 GB | Heavy (12 GB)Premium (8 GB) can do if players stay close. |
Estimated from 164 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 -Xmx7000M on 8 GB. Fabric 1.20.1 takes it in the java command (-Xmx), usually in the start script. RAM guide.
Horizons server requirements
| Java | Java 17 |
|---|---|
| Loader | Fabric for Minecraft 1.20.1 |
| CPU | Fast single-core speed (one main thread). With 164 mods, the first start takes minutes. |
| RAM | About 4.5–9 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 Horizons
Premium
8 GB RAM · planned launch price $30/month
At about 164 Fabric mods this is a mid-size pack, and 8 GB gives it room for the mods plus the chunks your players load.
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 Premium servers open.
More than 8 players, or lots exploring at once? Go up to Heavy (12 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 Horizons server on your own PC
What's specific to Horizons, 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.
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
java -jaron the Fabric 1.20.1 server launcher, then seteula=trueineula.txtif you accept Mojang's EULA (EULA step). With 164 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 Horizons on DSN
Once we relaunch (join the launch list), on DSN you'd install Horizons from the panel's Modrinth modpack installer (version 1.5), pick Java 17 on the Startup tab and accept the EULA in the console. No port forwarding.
How to play Horizons with friends
Each player installs Horizons version 1.5 with the Modrinth App or Prism Launcher, the same version as the server, and adds the server's address under Multiplayer.
Different versions of Horizons 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 Horizons
Can't keep up! Is the server overloaded? means ticks take longer than 50 ms; more RAM won't fix that once Horizons has enough (tick lag guide). For Horizons:
- 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.
Common Horizons crashes
What a Fabric 1.20.1 server running Horizons hits most. For any other error, paste the log into the free crash log analyzer.
- Wrong Java version. Horizons 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. - Out of memory. Horizons (164 mods on the server) needs about 4.5–5.5 GB for 1–3 players;
java.lang.OutOfMemoryErrormeans it ran out. Out-of-memory fix. - Client-only mod on the server. The Horizons 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 Horizons 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 Horizons past version 1.5, back up the world: see updating a modpack server without losing your world.
Bugs in Horizons itself go to its authors: Discord. Server problems on DSN: hello@dsnservers.com or Discord.
Packs like Horizons
More: all modpack guides and how to make a modded server.
Run Horizons on DSN when we relaunch.
Our pick, Premium: 8 GB, planned at $30/month.
DSN Servers isn't affiliated with Horizons or Modrinth. The pack's name, icon, summary and stats come from Modrinth's public API (checked October 4, 2026).