How to Install Deeper and Darker Mod 1.4.1 on NeoForge 1.21.1

Install the Deeper and Darker 1.4.1 JAR in a Minecraft 1.21.1 NeoForge profile, then launch the game.

Check the exact build before downloading

The direct file integrated on this website is deeperdarker-neoforge-1.21.1-1.4.1.jar. It is version 1.4.1 of Deeper and Darker for Minecraft 1.21.1 and the NeoForge loader. Treat those three values as one compatibility set. A JAR built for a different loader or Minecraft branch should not be mixed into this profile simply because the project name is the same.

Create or select a NeoForge 1.21.1 profile

Install and launch a Minecraft 1.21.1 NeoForge profile through the launcher or mod manager you already trust. Start the profile once before adding the mod. That first launch creates the normal game folders and gives you a clean point for troubleshooting if the profile itself fails.

Place the JAR in the mods folder

Download the file from the main button on this site. The button points to CurseForge rather than a rehosted mirror. Put the JAR inside the mods folder used by that exact NeoForge instance. Do not extract the JAR. If your launcher manages separate instances, use the instance folder shown by the launcher instead of assuming every profile shares the default .minecraft directory.

Launch and verify before opening an important world

Start the 1.21.1 NeoForge profile and confirm Deeper and Darker is present in the loaded mod list. If the loader shows an error, read the first relevant dependency or compatibility message in the log. Fix that requirement instead of downloading random “fix” files. Once the profile starts normally, make a world backup before using the mod in an established save.

Server installation basics

CurseForge lists Deeper and Darker as a Client & Server project. For a server, the safest pattern is to keep the server and participating clients aligned on Minecraft 1.21.1, NeoForge and the same Deeper and Darker release. Test a copy of the server world before updating a dimension or world-generation mod.

If Minecraft crashes after adding the file

Remove the new JAR and confirm the profile starts. Then restore Deeper and Darker alone, without unrelated new mods from the same batch. If that works, add the other mods back in small groups until the conflict returns. This reduces a large modpack problem to a smaller compatibility problem you can actually diagnose.

Related guides

Continue with the portal guide, Otherside guide or troubleshooting guide.