Minecraft server versions and Java
Which Java does this version need, and will the jar I just downloaded load on my server? The two questions usually come together, and the second fails without any error — which is why it eats days.
Java version required
21or newer
An older Java will not start it. A much newer Java normally does, but that is up to the server software rather than Minecraft.
Availability
Paper is available for 1.21.1
It accepts Bukkit / Spigot / Paper plugins.
Will the file I downloaded work?
Mods and plugins are two different things that both come as a .jar. Use the wrong kind and there is usually no error: the server boots and the content is simply missing.
running on Paper
No. Forge is a mod platform and Paper runs plugins — two separate systems that just share a file extension. Nothing loads, and you get no warning.
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Four Java boundaries
Minecraft's Java requirement has gone up four times. Those boundaries decide everything, even for releases newer than this page: any version past the last boundary needs Java 21.
- Java 81.7 through 1.16.5
- Java 161.17 and 1.17.1
- Java 171.18 through 1.20.4
- Java 211.20.5 and everything after
A wrong Java does not produce a message saying so. Instead you get an unsupported class file version plus a number — 52 for Java 8, 60 for Java 16, 61 for Java 17, 65 for Java 21. That number is the Java the file was compiled for, not the Java you are running.
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Versions against server software
| Version | Java | Vanilla | Paper | Purpur | Spigot | Fabric | Forge | NeoForge | Quilt |
|---|---|---|---|---|---|---|---|---|---|
| 1.21.4 | 21+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | — |
| 1.21.1 | 21+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | — |
| 1.20.6 | 21+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | — |
| 1.20.4 | 17+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | — |
| 1.20.1 | 17+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| 1.19.4 | 17+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | — | ✓ |
| 1.19.2 | 17+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | — | ✓ |
| 1.18.2 | 17+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | — | ✓ |
| 1.17.1 | 16+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | — | — |
| 1.16.5 | 8+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | — | — |
| 1.15.2 | 8+ | ✓ | ✓ | — | ✓ | ✓ | ✓ | — | — |
| 1.14.4 | 8+ | ✓ | ✓ | — | ✓ | ✓ | ✓ | — | — |
| 1.13.2 | 8+ | ✓ | ✓ | — | ✓ | — | ✓ | — | — |
| 1.12.2 | 8+ | ✓ | ✓ | — | ✓ | — | ✓ | — | — |
| 1.11.2 | 8+ | ✓ | ✓ | — | ✓ | — | ✓ | — | — |
| 1.10.2 | 8+ | ✓ | ✓ | — | ✓ | — | ✓ | — | — |
| 1.8.9 | 8+ | ✓ | ✓ | — | ✓ | — | ✓ | — | — |
| 1.7.10 | 8+ | ✓ | — | — | ✓ | — | ✓ | — | — |
Mods and plugins are different things
They share a .jar extension and both get dropped into a folder, and that is all they share. Plugins run on Bukkit-family servers — Spigot, Paper, Purpur — and alter the server without the client being involved, so players connect with a normal game. Mods run on Forge, NeoForge, Fabric or Quilt and change the game itself, so every player must have the same mods to join. A server runs one kind or the other, never both, and a file in the wrong folder causes no error at all.