> ## Documentation Index
> Fetch the complete documentation index at: https://help.freakhosting.com/llms.txt
> Use this file to discover all available pages before exploring further.

# UnsupportedClassVersionError on a Minecraft Server: Fix

> Fix UnsupportedClassVersionError on a Minecraft server: your Java is too old. Read the class file version, pick the right Java in Startup and restart.

`UnsupportedClassVersionError` means your Minecraft server, or a plugin or mod, was built for a newer Java version than the one your server runs. Fix it on FREAKHOSTING by opening **Startup**, choosing a newer Java under **Docker Image** (Java 25 for Minecraft 26.1 and newer, Java 21 for 1.20.5 to 1.21.11) and restarting the server.

| Difficulty | Time | Panel page |
| - | - | - |
| Beginner | 3 minutes | **Startup** |

***

## How to read the error

The error looks like this:

```
java.lang.UnsupportedClassVersionError: ... has been compiled by a more recent version
of the Java Runtime (class file version 69.0), this version of the Java Runtime only
recognizes class file versions up to 65.0
```

The first number is the Java the file needs. The second is the Java your server has.

| Class file version | Java version |
| - | - |
| 52.0 | Java 8 |
| 60.0 | Java 16 |
| 61.0 | Java 17 |
| 65.0 | Java 21 |
| 69.0 | Java 25 |

In the example, the file needs Java 25 (69.0) and the server runs Java 21 (65.0).

***

## Which Java does my Minecraft version need?

| Minecraft version | Java version |
| - | - |
| 26.1 and newer | Java 25 |
| 1.20.5 to 1.21.11 | Java 21 |
| 1.18 to 1.20.4 | Java 17 |
| 1.17 to 1.17.1 | Java 16 |
| 1.12 to 1.16.5 | Java 8 |

Check your version in **Version Changer** (status line **Currently installed: …**).

***

## How to fix it

**1. Open Startup**

Click **Startup** in the sidebar.

**2. Pick a newer Java**

Under **Docker Image**, choose the Java version from the tables above. The choices are Java 25, 21, 18, 17, 16, 11 and 8.

![Startup page in the FREAKHOSTING Game Panel with the Docker Image drop-down listing Java versions from 25 to 8](https://mintcdn.com/freakhostingltd/oRNjFa_9Ix118Tkc/images/games/minecraft/mc-startup.png?fit=max\&auto=format\&n=oRNjFa_9Ix118Tkc\&q=85\&s=39dc5d0d72a5d47e55c85f626d042f73)

Choose the Java version under Docker Image

**3. Restart**

Restart the server and watch the console. The error should be gone.

> [!TIP]
>
> **Version Changer** picks the right Java for you when you install a version. You usually see this error after uploading your own server jar, or after installing a plugin or mod made for a newer Minecraft version.

***

## What if a plugin or mod causes it?

If the error names a plugin or mod rather than the server, that file is made for a newer Minecraft (and Java) than your server. Don't just raise Java: the plugin or mod probably won't work on your Minecraft version either. Instead:

1. Open **Plugins** or **Mods** > **Installed** and delete it, or switch it off.
2. On **Browse**, install a version listed under **Versions for this server**.
3. Restart.

***

## Frequently asked questions

### What does "class file version 65.0" mean?

It means Java 21. A file with class file version 65.0 needs Java 21 or newer to run.

### Can I always use the newest Java?

Newer Minecraft versions need newer Java, but very old versions and some old modpacks only start on Java 8. Use the version in the table.

### I changed Java and now the server won't start. What now?

Set **Docker Image** back to the previous Java and restart. Then check the error in **Logs**: it may be a different problem. See [server crashing](https://help.freakhosting.com/games/minecraft/minecraft-server-crashing-or-out-of-memory.md).

### Does UnsupportedClassVersionError affect players?

No. It's a server error. Players can't join until the server starts, but nothing on their side needs changing.

***

## Related guides

> **[Minecraft server guide](https://help.freakhosting.com/games/minecraft/minecraft-server-hosting-guide.md)**
>
> Every Minecraft guide in one place.

> **[Startup flags and Java](https://help.freakhosting.com/games/minecraft/optimizing-server-startup-flags.md)**
>
> The Startup page explained.

> **[Change your server version](https://help.freakhosting.com/games/minecraft/changing-your-minecraft-server-version.md)**
>
> Version Changer sets Java for you.

> **[Server crashing](https://help.freakhosting.com/games/minecraft/minecraft-server-crashing-or-out-of-memory.md)**
>
> Other start-up errors.

> [!NOTE]
>
> **Tested by the FREAKHOSTING team** on our Game Panel on 29 October 2026 (Minecraft 26.1, Paper and Fabric). Java requirements checked against the official [Minecraft 26.1 release notes](https://www.minecraft.net/en-us/article/minecraft-java-edition-26-1).

***

> [!NOTE]
>
> ### Need Extra Help?
>
> If you encounter any issues, our support team is ready to assist:
>
> * **Live Chat:** Quick assistance via our website.
> * **Support Ticket:** [Open a Ticket](https://freakhosting.com/clientarea/submitticket.php)
> * **Discord:** [Join our Community](https://discord.gg/freakhosting)
> * **Email:** [support@freakhosting.com](mailto:support@freakhosting.com)

> [!TIP]
>
> ### Save on Your Hosting
>
> Ready to upgrade your hosting? Use code **KB20** at checkout for **20% off** your first order!

***

**Last Updated:** October 2026


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