1. Match your profile
Open the version checker and select the Minecraft version you intend to run. The captured releases use Fabric for 26.3 and 26.2, NeoForge for 1.21.1, and Forge for 1.20.1. An installed loader with the wrong name or game version will not work.
2. Gather exact dependencies
The Modrinth version metadata lists GeckoLib as required on all captured files. Those Fabric builds also list Fabric API; its older 26.2 file lists LambDynamicLights as required, while 26.3 lists it as optional. The newer 26.2 Fabric 1.0.2 author file on CurseForge has not had its dependency matrix verified here, so do not transfer the older file’s list to it. Check the exact author file page before installing.
3. Install and test
Create a fresh profile and back up worlds. Put the matching mod and dependency .jar files into that profile’s mods folder, launch once, and check the mod list. For multiplayer, the project metadata marks both client and server as required, so install matching versions on both sides.
Aternos and other servers
First check whether Aternos lists the exact author mod and a file matching your Minecraft version and loader; this site has not verified Mielon’s current Aternos catalog availability. Aternos supports selected CurseForge and Modrinth mods but does not allow arbitrary Java mod .jar uploads on its free service. If the exact file is absent, do not assume a nearby version works.
On any modded server, match the server and client Minecraft version, loader, mod file, and required dependencies. Aternos publishes separate instructions for installing the server loader and dependencies.
4. Recover from errors
If startup fails, compare the first missing dependency or loader mismatch in the log with the exact release metadata. Remove duplicate or older .jar files before trying again. Use the troubleshooter for a guided path.