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

# Building Paper from Source

> Learn how to compile Paper from source code

This guide walks you through building Paper from source code. Paper requires JDK 21 and an internet connection to compile.

## Prerequisites

<Warning>
  Paper requires **JDK 21** to build. The build system uses Gradle's Toolchains feature, which can automatically provision JDK 21 for compilation if you have JRE 17 or later installed.
</Warning>

Before you begin, ensure you have:

* **Git** - Version control system
* **JDK 21 or later** - [Adoptium](https://adoptium.net/) provides builds for most operating systems
* **Internet connection** - Required for downloading dependencies

### Windows Users

<Note>
  If you're on Windows, it's highly recommended to use **WSL 2** (Windows Subsystem for Linux) for significantly faster build times.
</Note>

WSL 2 is available on Windows 10 version 2004 (build 19041) or higher. You can check your version by running `winver`.

To set up WSL 2:

1. Follow the [official WSL installation guide](https://learn.microsoft.com/en-us/windows/wsl/install)
2. Install Ubuntu from the Microsoft Store
3. Install required tools: `sudo apt-get update && sudo apt-get install git -y`
4. Install a Java 21 JDK from [Adoptium](https://adoptium.net/)

## Build Steps

<Steps>
  <Step title="Clone the repository">
    Clone the Paper repository to your local machine:

    ```bash theme={null}
    git clone https://github.com/PaperMC/Paper.git
    cd Paper
    ```
  </Step>

  <Step title="Apply patches">
    Apply Paper's patches to create the modified Minecraft source:

    <CodeGroup>
      ```bash Linux/macOS theme={null}
      ./gradlew applyPatches
      ```

      ```bash Windows (without WSL) theme={null}
      gradlew applyPatches
      ```
    </CodeGroup>

    This command applies Paper's modifications to the Minecraft source files. The process may take several minutes on the first run.
  </Step>

  <Step title="Build the server">
    Compile Paper into a runnable JAR file:

    <CodeGroup>
      ```bash Linux/macOS theme={null}
      ./gradlew createMojmapBundlerJar
      ```

      ```bash Windows (without WSL) theme={null}
      gradlew createMojmapBundlerJar
      ```
    </CodeGroup>

    <Note>
      The first build will download all necessary dependencies and may take 5-15 minutes depending on your internet connection and hardware.
    </Note>
  </Step>

  <Step title="Locate the compiled JAR">
    After a successful build, find your compiled server JAR at:

    ```
    paper-server/build/libs/paper-server-<version>.jar
    ```

    This JAR file is ready to run as a Minecraft server.
  </Step>
</Steps>

## Build Outputs

Paper's build system can create several different JAR formats:

| Build Task                 | Output Location            | Description                                             |
| -------------------------- | -------------------------- | ------------------------------------------------------- |
| `createMojmapBundlerJar`   | `paper-server/build/libs/` | Mojang-mapped bundler JAR (recommended for development) |
| `createReobfBundlerJar`    | `paper-server/build/libs/` | Reobfuscated bundler JAR (production)                   |
| `createMojmapPaperclipJar` | `paper-server/build/libs/` | Mojang-mapped Paperclip JAR                             |
| `createReobfPaperclipJar`  | `paper-server/build/libs/` | Reobfuscated Paperclip JAR (production)                 |

<Note>
  **Mojmap vs Reobf:** Mojang-mapped JARs use readable names for better debugging. Reobfuscated JARs are optimized for production use.
</Note>

## Docker Build

You can also compile Paper using Docker with Adoptium's official images:

```bash theme={null}
docker run -it -v "$(pwd)":/data --rm eclipse-temurin:21.0.5_11-jdk bash
```

Once inside the container:

```bash theme={null}
cd /data
./gradlew applyPatches
./gradlew createMojmapBundlerJar
```

## Troubleshooting

### Build fails with "JAVA\_HOME not set"

Ensure JDK 21 is installed and `JAVA_HOME` environment variable points to your JDK installation:

```bash theme={null}
export JAVA_HOME=/path/to/jdk-21
```

### Out of memory errors

The build system automatically allocates 1GB of memory for compilation. If you encounter OOM errors, increase available system memory or close other applications.

### Slow build times on Windows

Switch to WSL 2 for significantly faster build performance. Native Windows builds can be 5-10x slower than WSL 2.

## Next Steps

* [View available Gradle tasks](/advanced/gradle-tasks)
* [Set up your development environment](/advanced/development-setup)
* Read the [CONTRIBUTING.md](https://github.com/PaperMC/Paper/blob/main/CONTRIBUTING.md) for patch development guidelines