How To Install Java 21 On Windows

Okay, here’s how you can install Java 21 (specifically the JDK – Java Development Kit) on Windows. The JDK includes everything you need to run Java applications (the JRE) plus the tools needed to compile and develop them.¹

As of April 2, 2025, Java 21 is the latest Long-Term Support (LTS) version, making it a good choice for general use and development.²

Step 1: Choose a JDK Distribution

You have several excellent options for obtaining OpenJDK builds (the open-source implementation of Java).³ Oracle also provides its own JDK.

• Adoptium (Eclipse Temurin): Very popular, community-supported, free, and rigorously tested builds of OpenJDK.⁴ Highly recommended for most users.
  • Download page: https://adoptium.net/temurin/releases/?version=21
• Oracle OpenJDK: Oracle also provides free OpenJDK builds (separate from the Oracle JDK).
  • Download page: https://jdk.java.net/21/
• Oracle JDK: Oracle’s official commercial build. As of JDK 17 and later (including 21), it’s under the “No-Fee Terms and Conditions” (NFTC) license, which allows free use, even for production and commercial purposes.⁵ You just need to accept the license.
  • Download page: https://www.oracle.com/java/technologies/downloads/#jdk21-windows⁶
• Microsoft Build of OpenJDK: Microsoft’s build, often used with Azure or other Microsoft development tools.⁷
  • Download page: https://learn.microsoft.com/en-us/java/openjdk/download#openjdk-21
• Other distributions: Azul Zulu, Amazon Corretto, Red Hat build of OpenJDK, etc., are also available.⁸

For most users, Adoptium Temurin is an excellent and straightforward choice.

Step 2: Download the JDK Installer

1. Go to the download page of your chosen distribution (e.g., the Adoptium link above).
2. Look for the Java 21 or JDK 21 section.
3. Select Windows as the Operating System.
4. Choose the x64 Architecture (most modern Windows PCs).
5. Download the .msi (Installer) file. This is generally the easiest way for Windows users.

Step 3: Run the Installer

1. Once the .msi file is downloaded, double-click it to launch the installation wizard.
2. You will likely need administrator privileges. Accept the prompt if it appears.
3. Follow the steps in the wizard. You can usually accept the default settings.
   • Important: Pay attention during installation. Some installers (like Adoptium’s) offer options to:
     • Set JAVA_HOME variable: This is highly recommended. Allow the installer to do this if offered.
     • Add to PATH: Also highly recommended. This allows you to run java commands from any command prompt. Allow the installer to do this.
     • Associate .jar files (Optional).
4. Click “Install” and wait for the process to complete.
5. Click “Finish”.

Step 4: Verify the Installation

1. Open a new Command Prompt or PowerShell window. (It’s important to open a new one after the installation finishes so it picks up any environment variable changes).
2. Type the following command and press Enter: Bashjava -version
3. You should see output indicating Java version 21 (e.g., openjdk version "21.0.x"...).
4. Also check the Java compiler version: Bashjavac -version
5. This should also report javac 21.0.x.

If both commands work and show version 21, Java 21 is successfully installed and configured in your system’s PATH.

Step 5: Configure Environment Variables (If Necessary)

If the installer didn’t set the JAVA_HOME and PATH variables automatically, or if you need to manage multiple Java versions, you should set them manually.

1. Find the JDK Installation Directory: This is typically under C:\Program Files\. Examples:
   • Adoptium: C:\Program Files\Eclipse Adoptium\jdk-21.0.x.x-hotspot (replace x.x with the specific minor version)
   • Oracle JDK: C:\Program Files\Java\jdk-21
   • Microsoft OpenJDK: C:\Program Files\Microsoft\jdk-21.0.x.x-hotspot
   • Note down this full path.
2. Open Environment Variables:
   • Press Win + R, type sysdm.cpl, and press Enter.
   • Go to the Advanced tab.
   • Click the Environment Variables... button.
3. Set JAVA_HOME (System Variable):
   • Under the “System variables” section (recommended for all users), click New....
   • Variable name: JAVA_HOME
   • Variable value: Paste the full path to your JDK installation directory (e.g., C:\Program Files\Eclipse Adoptium\jdk-21.0.x.x-hotspot).
   • Click OK.
4. Edit Path (System Variable):
   • Under “System variables”, find the Path variable.
   • Select it and click Edit....
   • Click New.
   • Add the following entry: %JAVA_HOME%\bin
   • (Optional but recommended): Use the Move Up button to move this entry near the top, especially if you have other Java versions installed, to ensure Java 21 is prioritized.
   • Click OK on all open dialog boxes (Edit environment variable, Environment Variables, System Properties).

Step 6: Test Environment Variables

1. Open a NEW Command Prompt or PowerShell window (essential for the changes to take effect).
2. Verify java -version and javac -version again.
3. Verify JAVA_HOME is set: Bashecho %JAVA_HOME% This should print the path you set in Step 5.3.

You have now successfully installed Java 21 JDK on your Windows system!