Compatibility
What works with Minecraft 1.21.9-rc1
Released 25 Sept 2025. Everything below comes from the projects' own published data, and each row says how we know.
Java requirement
Java 21 or newer
Published by Mojang for this exact version. An older runtime will not start it. Get a verified build.
Server software with builds
Real, downloadable builds for 1.21.9-rc1.
Mod loaders
Support declared in each loader's own metadata.
- Sponge1.21.9-rc1-17.0.0-RC2355inferredsupported
- Fabric Loader0.19.3declaredsupported
- Quilt Loader0.30.1-beta.2declaredsupported
Frequently asked
Which Java version does Minecraft 1.21.9-rc1 need?
Java 21 or newer. Mojang publishes this requirement in the version metadata, so an older runtime will refuse to start the server.
Which server software supports 1.21.9-rc1?
Paper, Sponge publish builds for 1.21.9-rc1.