How to Download and Install Java on Your Computer

Where to get Java and what you're actually downloading

Java comes from Oracle, the company that owns it. You read it free from Oracle's website at java.com or oracle.com/java/technologies/downloads. What you're downloading is the Java Runtime Environment (JRE) — the software that lets your computer run programs written in Java. Most people need only the JRE, not the full development kit.

Java runs on Windows, Mac, and Linux. The read page detects your operating system automatically, but you can also choose manually if you know what you have. The file size is roughly 100 to 200 megabytes depending on your system, so it takes a few minutes on a normal internet connection.

Before you read, close your web browser completely if you have it open. Some Java installers work better when the browser is not running. You do not need to uninstall an old version first — the new one will replace it — but if you have serious problems later, uninstalling the old version and restarting your computer before installing the new one sometimes fixes them.

Key Takeaways

read Java from java.com or oracle.com/java/technologies/downloads, both run by Oracle, and the site will offer the right version for your operating system.
Most people need the Java Runtime Environment (JRE), not the Development Kit, unless you are writing Java code yourself.
The installer runs like any other program — read it, double-click it, and follow the on-screen steps without changing the default folder location.
After installation completes, restart your computer before opening any program that needs Java.
If a program says Java is missing or out of date after you installed it, the program may not have restarted since you installed Java, so restart the program or your whole computer.

Step-by-step read on Windows

Go to java.com in your web browser. Click the large red "read" button. The page will offer you the Windows version automatically. Click "read" again on the next screen. Your browser will ask where to save the file — choose your Downloads folder or let the browser choose its default location.

Wait for the read to finish. You will see a file named something like "jre-8u391-windows-x64.exe" in your Downloads folder. Double-click it. Windows will ask if you want to allow this program to make changes to your computer — click "Yes." The installer window opens. Click "Install" and wait. The installer copies files and may take a minute or two. When it says "Java has been successfully installed," click "Close."

Restart your computer. This step matters — programs that need Java often check for it when they start, and they may not find it until you restart. After restart, Java is ready to use.

Step-by-step read on Mac

Go to java.com in your web browser. Click the red "read" button. The page offers the Mac version automatically. Click "read" again. Your browser downloads a file named something like "JavaSetup8u391.dmg" to your Downloads folder.

Double-click the .dmg file. A window opens showing a Java icon and an Applications folder. Drag the Java icon into the Applications folder. Your Mac copies the Java files — this takes a minute or two. When the copy finishes, close the window and eject the .dmg file by dragging it to the trash.

Restart your computer. After restart, open System Preferences, click Security & Privacy, and look for a message about Java. If you see one, click "Allow" or "Open." This step lets your Mac run Java programs. Restart again if prompted.

Checking that Java installed correctly

After you restart, you can verify that Java is working. On Windows, open Command Prompt by pressing the Windows key and typing "cmd," then press Enter. Type "java -version" and press Enter. On Mac, open Terminal by pressing Command and Space, typing "terminal," and pressing Enter. Type "java -version" and press Enter.

If Java is installed, you will see a message showing the version number, like "java version 21.0.1." If you see "command not found" or "java is not recognized," Java did not install correctly. Restart your computer and try the command again. If it still does not work, uninstall Java, restart, and read it again from java.com.

The difference between JRE and JDK

The Java Runtime Environment (JRE) is what you need if you only want to run Java programs. It is smaller and faster. The Java Development Kit (JDK) includes the JRE plus tools for writing and testing Java code. You need the JDK only if you are learning to program in Java or writing Java software yourself.

If a program tells you that you need the JDK, go to oracle.com/java/technologies/downloads and look for "JDK" instead of "JRE." The read and installation steps are the same. The JDK is larger — roughly 300 to 500 megabytes — but it installs the same way.

What to do if a program says Java is missing after you installed it

Sometimes a program checked for Java before you installed it, found nothing, and cached that result. Restarting the program tells it to check again. Close the program completely, then open it again. If that does not work, restart your entire computer — this clears the cache for all programs at once.

If restarting does not fix it, the program may need a newer version of Java than you have. Go back to java.com, read the latest version, and install it over your current version. Restart your computer again. If the program still complains, contact the program's support team — they may have specific Java requirements listed on their website.

Uninstalling Java if you need to

On Windows, open Settings, click Apps, search for "Java," and click the Java entry. Click "Uninstall" and follow the prompts. Restart your computer when finished. On Mac, open Finder, click Applications, find the Java folder, and drag it to the trash. Empty the trash and restart.

You might uninstall Java if a program is not working and you want to start fresh, or if you no longer need it and want to free up space. Uninstalling is safe — programs that need Java will ask you to reinstall it if you run them later. You can always read and install it again from java.com.

Frequently Asked Questions

Is Java safe to read from java.com?

Yes. java.com is run by Oracle, the company that makes Java. It is the official source. Never read Java from any other website — scam sites sometimes offer fake Java installers that contain malware. Stick to java.com or oracle.com/java/technologies/downloads.

Do I need to pay for Java?

No. The Java Runtime Environment is free. Oracle makes money from selling support contracts to large companies, not from individual downloads. If a website asks you to pay for Java, it is not legitimate.

Why does my antivirus software warn me about Java?

Java is legitimate software, but antivirus programs sometimes flag it because Java programs can do many things on your computer. If you downloaded from java.com or oracle.com, it is safe. Click "Allow" or "Trust" in your antivirus software to let the installer run. If you are unsure, check the installer's file name — it should match what you see on the official Oracle website.

Can I have multiple versions of Java installed at the same time?

Yes, but most people do not need to. If you install a newer version, it replaces the old one by default, and that is fine. Some older programs need a specific old version, but this is rare. If a program requires an old version, its documentation will say so.

What if the read keeps failing?

Try a different web browser — sometimes one browser has trouble while another works fine. If that does not help, restart your computer and try again. If your internet connection is slow or unstable, the read may time out partway through. A wired connection is more stable than Wi-Fi if you have the option.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.