Minecraft versions, Java, and what actually runs
Two questions, answered together because they are usually tangled: which Java a version needs, and whether the jar you just downloaded will load on the server you have. The second one fails silently, which is why it costs people days.
Java version required
21or newer
Older Java will refuse to start. Much newer Java usually works, but the server software is what decides that, not Minecraft.
Availability
Paper is available for 1.21.1
It accepts Bukkit / Spigot / Paper plugins.
Will what I downloaded work?
Mods and plugins are different things that both arrive as a .jar file. Putting the wrong one in usually produces no error at all — the server starts, and the content simply is not there.
running on Paper
No. Forge produces mods and Paper runs plugins — they are different systems that happen to share a file extension. Nothing will load, and nothing will warn you.
The Java rule in four lines
Minecraft has raised its Java requirement four times. Everything follows from these boundaries, including releases newer than this page — if your version sits above the last boundary, it 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
When the Java version is wrong the server does not say so in those words. It reports an unsupported class file version and a number: 52 means Java 8, 60 means Java 16, 61 means Java 17, and 65 means Java 21. The number it names is the Java the file was built for, not the one you have.
Every version against every 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 not the same thing
Both arrive as a .jar file and both go in a folder, which is where the similarity ends. Plugins run on Bukkit-family servers — Spigot, Paper, Purpur — and change server behaviour without the client knowing anything about it, so players join with an unmodified game. Mods run on Forge, NeoForge, Fabric or Quilt, change the game itself, and every player needs the same mods installed to connect at all. A server can run one family or the other, not both, and putting the wrong file in the wrong folder produces no error whatsoever.