# Setting Up a Development Environment

> For the complete documentation index, see [llms.txt](https://plugins.jetbrains.com/docs/intellij/llms.txt).

Procedure: Preliminary Steps

> **Warning: Installing Plugin DevKit plugin**
> Plugin DevKit plugin must be installed from JetBrains Marketplace ([Plugin Homepage](https://plugins.jetbrains.com/plugin/22851-plugin-devkit)) as it is not bundled since version 2023.3.

Use the following checklist to ensure that the environment is ready for custom theme development:

1. [IntelliJ IDEA](https://www.jetbrains.com/idea/download/) is installed.

2. Plugin DevKit plugin is installed and [enabled in IntelliJ IDEA](https://www.jetbrains.com/help/idea/managing-plugins.html).

3. IntelliJ IDEA CE source code is checked out. (Optional)

This step is needed only for debugging the IntelliJ Platform code. See [Get IntelliJ IDEA CE Source Code](#get-intellij-idea-ce-source-code) for more details.

4. IntelliJ Platform SDK is [configured](#configuring-intellij-platform-plugin-sdk).

## Get IntelliJ IDEA CE Source Code

Getting the IntelliJ IDEA CE source code is not a requirement for theme development as debugging the platform code while developing a theme is a rare situation. When developing a plugin that extends IDE behavior or investigating how some components work internally, having sources makes debugging much more straightforward.

For detailed instructions on how to check out the code efficiently, refer to the Getting IntelliJ Platform section of the [IntelliJ Platform README file](https://github.com/JetBrains/intellij-community/tree/idea/263.7307.200/README.md). Note that building the checked-out sources is not required in this case.

## Configuring IntelliJ Platform Plugin SDK

> **Tip:**
> For more information about SDKs, see the [SDKs section](https://www.jetbrains.com/help/idea/working-with-sdks.html) in the IntelliJ IDEA Web Help.

### Download IntelliJ-Based IDE

To see the effects of the developed plugin in a real IDE, it is required to run the plugin in an [IDE development instance](ide-development-instance.html). In most cases, it is enough to download and use [IntelliJ IDEA](https://www.jetbrains.com/idea/download/). If it is required to style components used only in a specific IDE like GoLand or WebStorm, they can also be used as SDK, but debugging the core code will only work with the IntelliJ IDEA.

### Add JDK and IntelliJ Platform Plugin SDK

The first step of configuring a theme plugin SDK is adding the JDK.

> **Note: IDE and Java Versions**
> Java version must be set depending on the target [platform version](build-number-ranges.html#platformVersions).
>
>
>
>
> 2026.2+
> : Java 25
>
>
> 2024.2+
> : Java 21

Procedure: Add JDK

1. Go to `File | Project Structure | Platform Settings | SDKs`.

2. Click the Add button (+).

3. If the required JDK is installed on the machine, and it is detected, select it from the Detected SDKs list. If the JDK is not detected, select the Add JDK... option and choose the installation folder.

If the required JDK is not installed on the machine, the simplest option is using Download JDK... and choosing the distribution options.

4. Click the Apply button.

The second step is adding IntelliJ Platform Plugin SDK that will use the JDK configured in the first step.

Procedure: Add IntelliJ Platform Plugin SDK

1. Go to `File | Project Structure | Platform Settings | SDKs`.

2. Click the Add button (+).

3. Select the Add IntelliJ Platform Plugin SDK from disk... option.

4. Choose the installation folder of the IDE [downloaded previously](#download-intellij-based-ide).

> **Tip:**
> On macOS, in the file chooser, select `/Applications/` and switch the view to Show items as: List. Then, expand the IDE item and select the `Contents` folder.

5. In the Select Internal Java Platform dialog, select the JDK configured in the [previous step](#add-jdk) and click the OK button.

6. In the added SDK, specify the Sandbox Home directory.

See [The Development Instance Sandbox Directory](ide-development-instance.html#the-development-instance-sandbox-directory) for details.

7. If debugging is required, select the Sourcepath tab, click the Add button (+) and select the root folder of [the checked-out sources](#get-intellij-idea-ce-source-code).

8. Click the Apply button.