Server won't start or crashes right away?
If your Minecraft server flips straight back to offline after starting, or never comes up at all, the cause is almost always visible in the startup log — you just need to know where to look.
Finding the log: Open your server in the mcfreehost panel and switch to the Console tab. It shows the full output of the last start attempt from top to bottom. The interesting part is usually the last section before the crash — look for lines containing ERROR, FATAL or Exception.
By far the two most common reasons a Fabric, Forge or modpack server fails to start both revolve around mods: either a mod ended up on the server that doesn't belong there, or a mod dependency is missing or doesn't match the Minecraft version. Both show up as recognizable log patterns — this guide shows you what they look like and how to fix them.
Error class 1: A client mod ended up on the server
What it looks like in the log:
[main/ERROR]: Failed to start the minecraft server
java.lang.RuntimeException: Could not execute entrypoint stage 'main' due to errors, provided by 'modname'
If your log shows exactly this line (or something very close to it), the diagnosis is clear: one of your installed mods is a client-only mod — it belongs on the player's PC, not on the server.
Why this happens
Many mods exist only for the client (your game window) because they provide purely visual or convenience features that the server simply cannot run. If you install such a mod in the server's /mods folder anyway, Fabric or Forge tries to load its entry point (entrypoint) — and fails, because the mod expects client classes that don't exist on a server process (no graphics, no window). The whole server then crashes, not just that one mod.
Common client-only mods that repeatedly end up on servers by mistake:
| Category | Examples | Why client-only |
|---|---|---|
| Minimaps | Xaero's Minimap, JourneyMap (client mode) | Renders the map inside the game window |
| Shaders/graphics | Iris, Oculus, pure visual mods | Only changes the local rendering |
| HUD/UI | Better-HUD mods, inventory overlays | Shows extra info in the client interface |
| Sound/music packs | Client-side ambient sound mods | Only plays audio locally |
How to fix it
- Read the mod name from the log line — right after
provided by '...'you'll find the technical mod slug (e.g.xaerominimap). - Open the file manager — in the panel, go to Files and switch to the
/modsfolder. - Find and delete the matching
.jarfile — filenames usually contain the mod name; if unsure, search the mod slug online to confirm the official file name. - Restart the server — via the power button in the panel.
Check the log again afterwards: if another Could not execute entrypoint error shows up for a different mod, repeat the steps — it's common for several client mods to end up in the wrong folder together (e.g. when a whole local mods folder was uploaded as-is instead of selecting only the server-compatible mods).
Tip: On modding platforms (Modrinth, CurseForge) every mod page has an Environment field showing Client, Server or Client and Server. Only mods marked Server or Client and Server belong in the server's /mods folder.
Error class 2: Mod dependencies and registry errors
If your server starts without the entrypoint line from above, but instead you see errors while loading registries (items, blocks, recipes) or messages about missing dependencies, one of the following is usually the cause:
- Missing Fabric API / Forge library — many mods build on a base library (e.g. Fabric API). If it's missing from
/mods, every mod that requires it fails to load. - Incompatible Minecraft version — a mod built for MC 1.20.4 won't reliably load on a 1.20.1 server (and vice versa), even when the version numbers look similar.
- Mod pairs that belong together — some mods consist of two parts (e.g. a main mod plus a separate compatibility addon). If one of the two is missing, the other's registry initialization fails.
What to do
- Check versions — compare your server's Minecraft version (Panel → Configuration) with the version each mod was built for according to its download page. On Fabric/Forge the loader also has to match (Fabric mods don't run on Forge and vice versa, and NeoForge is its own loader again).
- Install the missing dependency — if the log mentions something like "requires fabric-api" or a similar dependency error, download exactly that library in the matching version and place it in
/modsas well. - Bisect if needed — if you can't pin down a clear cause, move half of your mods out of
/modsinto another folder (e.g./mods-disabled) as a test and restart. If the server now starts, the error is in the removed half — repeat the process with that half until you've isolated the single offending mod. - Restart the server and check the log again.
This error class often needs a bit more patience than error class 1, because the error message less often names the exact mod — the bisect procedure from step 3 is reliable regardless, even when the log itself gives little away.
World or data errors: when to contact us
Not every startup error is mod-related. If your log instead shows a line like:
Unable to read or access the world gen settings file! Falling back to the default settings with a random world seed.
or more generally "Unable to read or access ..." referring to world or configuration files, that points to a corrupted world or data directory — this is not a mod issue and can't be fixed by removing mods.
In that case: contact our support via the ticket system in the panel and include the exact log excerpt. Please don't delete anything yourself in the file manager before support has looked at the log — that only makes diagnosis harder.
FAQ
How do I recognize client-only mods before uploading them?
Every mod's download page (Modrinth, CurseForge) shows an Environment field with the values Client, Server or Client and Server. Only mods marked Server or Client and Server belong in the server's /mods folder. If it only says Client, install the mod locally in your game client only, never on the server.
Why did my server suddenly stop starting after a mod update?
Mod updates sometimes change their Minecraft version requirement or their dependencies without you actively noticing — especially if a modpack creator has enabled automatic updates. Check the exact error message in the log: if it refers to a registry or a missing dependency, error class 2 in this guide will help. The safest approach is to create a backup via the panel before any major mod update.
Do I have to test every mod individually if I can't find the culprit?
Not individually — bisect your mod list instead (see error class 2). With, say, 40 mods, that means at most around 6 restarts in the worst case to narrow down the single faulty mod, instead of 40 individual tests.
Can a client mod on the server also corrupt data?
No. A client-only mod that ends up on the server only prevents the server process from starting — it doesn't touch your world and doesn't corrupt any data. As soon as you remove the .jar file from /mods, the server starts normally again with your world unchanged.