To run Meteor Rejects smoothly on Minecraft 1.21.1, you must assemble the correct mod stack to prevent startup crashes.
Features that were originally from other clients and ported over.
As of now, the official Rejects repository is frequently updated to track the latest "dev" builds of Meteor. To run Rejects on 1.21.1, you generally cannot use an old .jar file from 1.20 or 1.19; you must source a build specifically compiled for the 1.21.x architecture. How to Install Meteor Rejects for 1.21.1
Launch Minecraft and open the Meteor GUI (default key: Right Shift ) to see the new modules. Common Issues