A mod is made for a different Minecraft version

A mod is built for one Minecraft version or a short range of versions. If you add a mod made for another version, Fabric, Forge and NeoForge refuse to start and name the mod. Install the build of that mod made for your server's Minecraft version, or remove it.

What you see

The server stops while it starts, and the Why your server stopped box on Overview and above the Console says one of these:

• A mod is made for a different Minecraft version. with It needs Minecraft and the versions it accepts, and sometimes and this server runs and your version.
• The mod and a name failed to start. with It may be made for a different Minecraft version, or clash with another mod. Check that it is the version made for this server, or remove it.

Both offer Find and the mod's name, which opens Modding.

In the Console, the loader's own lines name the mod:

• Fabric: a line that says the mod requires a version of minecraft, with which is missing! or but only the wrong version is present:.
• Forge and NeoForge: a block that starts Missing or unsupported mandatory dependencies: and a line with Mod ID: 'minecraft', Requested by: and the mod, Expected range: and Actual version:.
• A failed start: Mixin apply for mod and the mod's id, then failed.

Fix it

1. Note the mod's name from the box or the console line. Fabric gives the mod's name, Forge and NeoForge its id, which is often close to its file name in mods.
2. Open Modding and the Mods tab. Your server's version shows as (your server) in the Minecraft version filter.
3. Find the mod under Installed, open its menu (the three dots at the end of its row) and choose Choose a version. Pick a build for your Minecraft version. See How to install mods on Forge, Fabric and NeoForge.
4. If there is no build for your version, remove the mod: Uninstall in its menu on Installed, or delete its file from mods in Files.
5. Start the server and watch the Console. Fix the next mod the same way if another one is named.

If you added the mod yourself

A mod you uploaded through Files or SFTP may show under Installed as Not recognized - installed manually or renamed. The panel cannot offer other versions of it. The mod's own page lists the Minecraft versions each file is for: download the file for your version, delete the old file from mods in Files, and upload the new one.

If it says failed to start

A mod can fail to start for a reason other than the version: two mods that change the same part of the game can clash. If the mod is already the right build for your Minecraft version:

1. Remove the mod you added most recently, then start the server.
2. If it starts, the two mods do not work together. Look on both mods' pages for a fix or a note about the other mod.

Good to know

• Changing your server's Minecraft version to fit one mod changes it for every mod, and a world cannot go back to an older version. See Your Minecraft world cannot go back to an older version.
• Players may need the matching build in their own game too: How to get your players ready for a modded Minecraft server.
• Other causes the panel names: How to see why your Minecraft server stopped.