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

# Host a Java App or Bot (JAR)

> Deploy a Java app or Discord bot on Square Cloud: build an executable JAR, set MAIN to the .jar file, and Square Cloud starts it with java -jar on JDK 25.

The Java runtime runs executable JAR files on JDK 25: bots, workers, APIs and websites. You build the JAR on your machine, and Square Cloud starts it with `java -jar`.

## Before you begin

* A Java Development Kit (JDK) on your machine. If you don't have one yet, you can download Eclipse Temurin from [Adoptium](https://adoptium.net).
* A Square Cloud account: [sign up](https://squarecloud.app/en/signup) with your email or GitHub.
* An active plan. See the [plans](https://squarecloud.app/en/pricing) and pick the one that fits your project.

## Configure Square Cloud

<Note>
  If you upload your application through the dashboard, you can skip this section: the dashboard creates the `squarecloud.app` configuration file for you.
</Note>

<Card title="Configuration file reference" icon="link" href="/en/getting-started/config-file">
  The `squarecloud.app` file tells Square Cloud how to run your application: its main file, memory, runtime version, name and, for a website, its subdomain.
</Card>

Point `MAIN` to your JAR. A complete configuration file for each kind of app:

<Tabs>
  <Tab title="Bot or worker">
    ```systemd squarecloud.app theme={"system"}
    MAIN=app.jar
    MEMORY=512
    VERSION=recommended
    DISPLAY_NAME=My bot
    ```
  </Tab>

  <Tab title="Website or API">
    ```systemd squarecloud.app theme={"system"}
    MAIN=app.jar
    MEMORY=1024
    VERSION=recommended
    DISPLAY_NAME=My API
    SUBDOMAIN=my-api
    ```
  </Tab>
</Tabs>

`MAIN` accepts up to 32 characters. For a longer path, replace it with `RUNTIME=java` and `START=java -jar <path-to-your.jar>`.

## What Square Cloud runs

* If the `START` field is not defined in the configuration file, Square Cloud will execute `java -jar MAIN`, where the file specified in `MAIN` is the JAR file. If the `START` field is defined, the value in it will be executed directly. For more information about configuration file parameters, visit [configuration parameters](/en/getting-started/config-file#configuration-parameters).

### Port and host for websites and APIs

Square Cloud sets the `PORT` environment variable to `80`. Your server must listen on that port and on all network interfaces (`0.0.0.0`). With Spring Boot, set `server.port=${PORT:80}` in `application.properties`, as shown in the [Spring Boot guide](/en/tutorials/api/spring-boot).

## Prepare the project

Square Cloud does not compile Java projects: build an executable JAR on your machine and upload it.

* **Maven:** run `mvn package`; the JAR is written to `target/`. To bundle your dependencies into a single runnable JAR, use the Maven Shade or Assembly plugin and configure it to set `Main-Class`.
* **Gradle:** run `./gradlew build` (or `gradle build`); the JAR is written to `build/libs/`. To bundle your dependencies, use the Shadow plugin (`./gradlew shadowJar`) or set `Main-Class` in the `jar` task's manifest.

Check that the JAR starts with `java -jar your-app.jar` before uploading it. Compile it for Java 25 or earlier: the runtime cannot run classes built for a newer Java.

### Required files

* [`squarecloud.app`](/en/getting-started/config-file), at the root of the ZIP.
* Your executable JAR, set in `MAIN`. Its `META-INF/MANIFEST.MF` goes **inside** the JAR, not as a separate file, and must declare the `Main-Class` of your application.

<Warning>The configuration file (`squarecloud.app`) must be located at the root of the zip file. Otherwise, Square Cloud will not be able to find it during deploy.</Warning>

### What to leave out

* Your source code and build folders are optional: the JAR already contains the compiled application.

## Framework guides

<CardGroup cols={3}>
  <Card title="Spring Boot" icon="leaf" href="/en/tutorials/api/spring-boot" />
</CardGroup>

## Troubleshooting

<AccordionGroup>
  <Accordion title="no main manifest attribute" icon="file" iconType="solid">
    The JAR has no `Main-Class` in its manifest, so `java -jar` cannot start it. Build an executable JAR as described in [Prepare the project](#prepare-the-project).
  </Accordion>

  <Accordion title="UnsupportedClassVersionError" icon="code" iconType="solid">
    The JAR was compiled for a newer Java than JDK 25. Build it for Java 25 or earlier.
  </Accordion>
</AccordionGroup>

For other problems, see [Troubleshooting](/en/platform/troubleshooting).

## Deploy

### Via dashboard

<Steps>
  <Step title="Access the Upload Page">
    Access the [upload page](https://squarecloud.app/en/dashboard/new) and upload your project zip file.
  </Step>

  <Step title="Configure Your Environment">
    After uploading your zip, you will need to configure the name, main file or runtime environment and other settings for your project.\
    If you are uploading a web project, make sure to select "Web Publication" and set a subdomain to your project.
  </Step>

  <Step title="Deploy Your Project">
    Finally, click on the "Deploy" button to host your project on Square Cloud.\
    After deployment, you can monitor your project's status and logs from the dashboard.

    <Frame>
      <img src="https://cdn.squarecloud.app/docs/articles/dashboard/uploading.gif" alt="Uploading application to Square Cloud" style={{ borderRadius: "0.2rem" }} />
    </Frame>
  </Step>

  <Step title="Confirm Your App Is Live">
    Your first deploy usually takes less than a minute. In the [dashboard](https://squarecloud.app/en/dashboard), wait for your application status to show as running and check the logs for any startup errors.\
    If you deployed a website or API, open `https://<your-subdomain>.squareweb.app` in your browser: you should see your application responding. If you deployed a bot, send it a command to confirm it is online.
    <Tip>App not starting? See the [Troubleshooting guide](/en/platform/troubleshooting/app-wont-start) for the most common causes and fixes.</Tip>
  </Step>
</Steps>

### Via CLI

To use this method, your project needs a configuration file named `squarecloud.app` at its root. It tells Square Cloud how to run your application.

<Card title="Configuration file guide" icon="link" href="/en/getting-started/config-file">
  Learn how to create the `squarecloud.app` configuration file that defines your application's environment.
</Card>

<Steps>
  <Step title="Install the CLI">
    Install the [Square Cloud CLI](/en/cli-reference/installation). If you already have it, run the same command to update it:

    <CodeGroup>
      ```bash macOS, Linux, and WSL theme={"system"}
      curl -fsSL https://cli.squarecloud.app/install | bash
      ```

      ```bash Windows with npm theme={"system"}
      npm install -g @squarecloud/cli@latest
      ```
    </CodeGroup>
  </Step>

  <Step title="Log In">
    Run the command below. It opens your browser: approve the login there and the CLI is ready. There is no API key to copy. For scripts and CI, see [CLI authentication](/en/cli-reference/authentication).

    ```bash theme={"system"}
    squarecloud auth login
    ```
  </Step>

  <Step title="Upload Your Project">
    From your project folder, run the command below. The CLI zips the current folder, leaving out what [`squarecloud.ignore`](/en/getting-started/squarecloud-ignore) lists, and uploads it:

    ```bash theme={"system"}
    squarecloud upload
    ```

    To upload a zip you created yourself, pass it with `--file`:

    ```bash theme={"system"}
    squarecloud upload --file <path/to/zip>
    ```
  </Step>

  <Step title="Confirm Your App Is Live">
    Your first deploy usually takes less than a minute. Check your application status and logs directly from the terminal:

    ```bash theme={"system"}
    squarecloud app status
    squarecloud app logs
    ```

    If you deployed a website or API, open `https://<your-subdomain>.squareweb.app` in your browser: you should see your application responding. If you deployed a bot, send it a command to confirm it is online.
    <Tip>App not starting? See the [Troubleshooting guide](/en/platform/troubleshooting/app-wont-start) for the most common causes and fixes.</Tip>
  </Step>
</Steps>

## Next steps

<CardGroup cols={3}>
  <Card title="Environment variables" icon="key" href="/en/platform/environment-variables">
    Keep secrets and settings out of your code and read them at runtime.
  </Card>

  <Card title="Custom domain" icon="globe" href="https://help.squarecloud.app/en-us/article/how-to-set-up-your-own-domain-cnamedns-1fzbrgh/">
    Serve your app on your own domain, on the Standard plan and above.
  </Card>

  <Card title="Troubleshooting" icon="wrench" href="/en/platform/troubleshooting">
    Fix an app that does not start or a site that does not respond.
  </Card>
</CardGroup>

## Contact us

If you continue facing **technical difficulties**, our **specialized support team** is available to assist you. [**Contact us**](https://squarecloud.app/en/support) and we'll be happy to help you resolve any issue: support quality is a big part of why developers rate Square Cloud [**4.9/5 across 402 reviews**](https://www.trustpilot.com/review/squarecloud.app) on Google and Trustpilot.


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