Install modpacks through the Modpack Installer in the left sidebar. Pick your pack from the list, install it, then restart the server. You do not need to set a Java version. That is handled for you when the Server Type changes.
Nearly every "it won't start" problem after a modpack install comes down to one thing: the pack needs more RAM than your plan has.
Symptoms
- Server cycles between Starting and Offline after install
- Server crashes seconds after boot, or never fully loads
- Players get kicked immediately after joining
- Startup is extremely slow, or the world loads wrong (e.g. skyblock pack loading a normal world)
- RAM usage climbs steadily until the server dies
Why this happens
The most common root causes we see, in order:
- Not enough RAM. This is the big one. Heavy packs with 300 or more mods need 8GB to 10GB to boot reliably. On a 1GB to 4GB plan they will crash every time.
- Client-side mods in a server pack. Some packs include mods made only for the player's own game, like map mods, shader mods and tooltip mods. These crash a server.
- Wrong mod loader. Forge, NeoForge and Fabric are the three systems that load mods. A pack built for one will not run on another.
Before updating or reinstalling an existing modpack, take a Backup first, and avoid any "delete existing files" option during the download. Skipping this has cost players their entire inventories and world progress.
How to fix it
- Check the modpack's listed RAM requirement before installing. If you're unsure how much your pack needs, see how much RAM a modded server needs and size your plan accordingly.
- Open Modpack Installer from the left sidebar, find your pack, and install it. Your Java version is set for you when the Server Type changes, so there is nothing to configure there.
- Restart the server from the Restart button at the top of the page.
- Watch Console during boot. If it crashes or hangs, the crash log will usually name the offending mod or class: see how to read a Minecraft crash log for guidance.
- If the log mentions a mod version mismatch or missing dependency, check fixing missing dependency and mod conflict errors.
- If you're installing a modpack from your own files rather than the built-in library, follow uploading and installing a custom modpack instead.
- Once the server is Online, confirm with a friend that you can connect to the server.
Still stuck?
If the console log points to a specific mod, a corrupted world file, or a loader version you can't resolve yourself, open a support ticket with the crash log attached. Our team can identify incompatible mods, correct the mod loader version, or restore a backup if a modpack update wiped your world.
Did this solve it?
If you are still stuck, our team can look at your server directly.