// crash guide

Minecraft server crash: missing mod dependency

One of your mods needs another mod that isn't in the mods folder, or is there in the wrong version. The loader won't start the server until that's fixed. The missing piece is often a library like Fabric API, GeckoLib or Citadel.

Updated October 2026  ·  Forge, NeoForge, Fabric, Quilt

What the error looks like

The server stops before the world loads. Look in the console or logs/latest.log. Forge and NeoForge also write crash-reports/crash-<date>-fml.txt. The mod names below are examples.

Forge and NeoForge

[04Oct2026 14:02:11.482] [main/ERROR] [net.minecraftforge.fml.loading.ModSorter/LOADING]: Missing or unsupported mandatory dependencies:
	Mod ID: 'citadel', Requested by: 'alexsmobs', Expected range: '[2.6.0,)', Actual version: '[MISSING]'

The panel console shortens the logger to ne.mi.fm.lo.ModSorter. On NeoForge it starts with net.neoforged. The crash report says the same thing in plainer words:

Description: Mod loading error has occurred
...
-- MOD alexsmobs --
Details:
	Mod File: /.../mods/alexsmobs-1.22.9.jar
	Failure message: Mod alexsmobs requires citadel 2.6.0 or above
		Currently, citadel is not installed

If the last line shows a version number instead of not installed, the mod is there but in the wrong version. On NeoForge 1.21.1 the description line reads Mod loading failures have occurred; consult the issue messages for more details, and each section is headed Mod loading issue for: <mod ID>. The failure message uses the same words. Some mods add a Reason for the dependency: line under it.

Fabric

Fabric logs it under Incompatible mods found!:

net.fabricmc.loader.impl.FormattedException: Some of your mods are incompatible with the game or each other!
A potential solution has been determined, this may resolve your problem:
	 - Install fabric-api, any version.
More details:
	 - Mod 'Cobblemon' (cobblemon) 1.6.0+1.21.1 requires any version of fabric-api, which is missing!

If the dependency is there in the wrong version, the line says but only the wrong version is present: followed by the version you have. Older Fabric Loader versions, such as 0.14, say Mod resolution encountered an incompatible mod set! and Unmet dependency listing: instead. Quilt Loader words its errors differently, but it also names the missing mod ID.

Forge 1.12.2

net.minecraftforge.fml.common.MissingModsException: Mod tconstruct (Tinkers' Construct) requires [mantle@[1.12-1.3.3.49,)]

The first ID is the mod that asked. The one inside the brackets, before the @, is the missing mod. The crash report also has a Missing Mods: list.

What it means

Every mod jar lists the mods it needs, with a version range. That's META-INF/mods.toml on Forge, META-INF/neoforge.mods.toml on NeoForge 1.20.5+, fabric.mod.json on Fabric and quilt.mod.json on Quilt. At startup the loader checks every list and stops if something required is missing or out of range. That's on purpose. Otherwise you'd get a confusing crash later.

Read the error in three parts:

• The missing mod. The ID after Mod ID: on Forge and NeoForge, or after Install and of on Fabric. It's the internal ID, not the display name or file name.
• Who asked. Requested by: on Forge and NeoForge, or the first mod named on Fabric.
• The version. [MISSING], "not installed" or "which is missing" means it isn't there. A version number, or "only the wrong version is present", means it's there but too old or too new.

Forge and NeoForge ranges use Maven notation. [2.6.0,) means 2.6.0 or newer. [1.0,2.0) means 1.0 or newer, but below 2.0. Fabric writes ranges out in words.

The usual causes:

• You added a mod by hand but not its library.
• You updated a mod but not its library, or the other way round.
• The library is the build for another loader or Minecraft version. A Fabric build of GeckoLib won't load on Forge, so Forge counts it as missing.
• You deleted a library while clearing out client-only mods.
• On Fabric, Fabric API isn't installed. It's a separate jar from Fabric Loader, and most Fabric mods need it.

Common IDs and what to install

Common in these packs: mostly servers put together by hand rather than from a pack's server files. Cobblemon is a typical case: on Modrinth, Cobblemon 1.8.1 lists Fabric API as required on Fabric and Kotlin for Forge on NeoForge. The official Cobblemon packs for Fabric and NeoForge already include them. A server with Cobblemon added by hand needs them installed too.

How to fix it

1. Write down every ID and range in the error. Forge and Fabric usually list every problem at once, so fix them together instead of one restart at a time.
2. Take a backup. On DSN that's an on-demand backup from the panel.
3. Check what's already in mods/. Use the panel's file manager or SFTP. If the error shows a version number, the dependency is there in the wrong version. Delete that jar before you add the new one, or you'll have two copies. If the jar is there but the error still says it's missing, it's probably the build for another loader, or it's in a subfolder. A file ending in .jar.disabled doesn't load at all.
4. Download the right file. Search the mod on CurseForge or Modrinth. Filter by your exact Minecraft version and loader, then pick a version inside the range. Upload the jar straight into mods/, not a subfolder, and restart.
5. If the ID is forge, neoforge or fabricloader, update the loader to a version inside the range. Keep the same Minecraft version. On DSN's Pelican panel, run the one-click installer again and pick a newer build of the same loader.
6. If the ID is java, change the Java version. On DSN's Pelican panel, pick it from the Docker Image dropdown on the Startup tab.
7. If it's a modpack, use the official server pack. If you hand-added mods to a CurseForge or Modrinth pack, reinstall the pack at the version your players use. Then add extras one at a time, each with its dependencies. No server pack? Build one from the pack's own file list, which names every library.

Forge and NeoForge notes

A missing optional dependency is fine. But an optional one that's installed in an unsupported version also stops the server. The log shows it under Unsupported installed optional dependencies:, and the crash report says Mod <mod ID> only supports …. Update the optional mod to a version in the range, or remove it. NeoForge 1.20.1 runs most Forge 1.20.1 mods. From 1.20.2 on, you need the NeoForge build of each mod and library.

Fabric and Quilt notes

The "potential solution" block is often right, so start there. Fabric API file names include the Minecraft version, like +1.21.1. Match it to your server. If a line ends with which is disabled for this environment (client/server only)!, the dependency is client-only, so the mod that needs it probably doesn't belong on the server. See the client-only mod guide. Quilt runs most Fabric mods, so this applies there too.

How to check it's fixed

• Restart and watch the console. The ModSorter or Incompatible mods found! error should be gone.
• On Fabric, near the top of logs/latest.log, every loaded mod is listed after Loading N mods:. The dependency should be in that list.
• The server is up when you see Done (…s)! For help, type "help".
• A new error naming a different mod is normal. Libraries can need libraries too. Repeat the steps.
• Join from a client. Players need the same mods and versions as the server, apart from server-only mods.

Related crash guides

• Wrong mod loader or Minecraft versionA Fabric mod on Forge, or a mod for another Minecraft version.
• Client-only mod on a server"invalid dist DEDICATED_SERVER". Common after copying a client mods folder.
• Duplicate mods"Found duplicate mods". Two versions of one library in mods/.
• Wrong Java version"Unsupported class file major version". Also covers a Fabric java dependency.
• Updating a modpack serverUpdate the pack as a whole, so mods and their libraries move together.