How to Fix Fabric Loader Crashing on Startup

Find the Real Cause in the Log

A crash before the title screen almost always points to a mod problem, not the loader itself. Open your .minecraft folder and look in the logs directory for the latest log file. Search it for the words error, exception, or the name of a mod. The log usually names the mod that failed and the reason, such as a missing dependency or a version mismatch.

Common Fixes

Check that Fabric API is installed and matches your Minecraft version. Confirm every mod in the mods folder supports the same game version as your Fabric profile. Remove mods you recently added, then relaunch to see if the crash stops. If it does, add them back one at a time to isolate the culprit. Also make sure you are not mixing jars built for a different mod loader into the Fabric folder.

When the Loader Itself Is the Problem

If the crash happens with an empty mods folder, the issue is likely the profile or the loader version. Recreate the Fabric profile with the installer, or try a different loader build for your game version. Keep a backup of your world before making changes so troubleshooting never costs you progress.