Fix Forge Installer Not Opening with Java on Mac

Published On - December 27, 2025

Olivia Brown Blog

Installing Minecraft mods on Mac is usually a smooth process, but sometimes, users encounter a puzzling issue — the Forge Installer simply won’t open when clicked. This can be especially frustrating when you’ve already installed Java and expect everything to run smoothly. If you’re facing this problem, don’t worry — there are multiple tested solutions you can try to get the Forge Installer up and running on your Mac.

TL;DR (Too Long; Didn’t Read)

If your Forge Installer isn’t opening on your Mac, it’s likely due to a conflict with your Java version, file permissions, or Mac’s Gatekeeper security. Try reinstalling the correct version of Java (usually Java 8), ensuring the installer file is opened using Java, and bypassing Mac’s Gatekeeper if necessary. These steps will help you successfully launch and install Minecraft Forge.

Why the Forge Installer Might Not Be Opening

Let’s start by understanding why this issue happens. When users click the Forge Installer JAR file, macOS doesn’t always know how to handle the request properly. Unlike other operating systems, macOS places more restrictions on apps from the internet for security reasons. Here are some common causes:

  • Incompatible Java version: Forge often requires Java 8 specifically, not the latest Java version.
  • Incorrect file associations: macOS might try to open the JAR file with the wrong application.
  • Security restrictions: Apple’s Gatekeeper may block unsigned apps like Forge.
  • Damaged or incomplete JAR file: The installer may not have downloaded correctly.

Step-by-Step Solutions to Fix the Forge Installer

1. Install the Correct Version of Java

Most Forge installers are built with Java 8 in mind. Even if you have Java 17 or newer for running Minecraft, Forge setup often fails unless Java 8 is installed.

  1. Download and install Java 8 from Oracle’s Java 8 Archive or use Adoptium for OpenJDK variants.
  2. Restart your Mac after installation.
  3. Verify the version by opening the Terminal and running: 
    java -version

You should see an output like:

java version "1.8.0_281"

If it says something like ‘Java 17’ or ‘Java 11’, you’re using the wrong version.

2. Set Java 8 as the Default Version

macOS can have multiple versions of Java installed, but sometimes the system doesn’t default to the correct one. To ensure Java 8 is used:

  1. Use the following command in Terminal to see installed Java versions: 
    /usr/libexec/java_home -V
  2. Temporarily set Java 8 as default by running: 
    export JAVA_HOME=`/usr/libexec/java_home -v 1.8`

This change will last only for the current Terminal session, but it’s helpful when launching the Forge Installer manually.

3. Launch Forge Installer via Terminal

Sometimes, double-clicking the JAR file just doesn’t work. Opening it from the Terminal can provide error messages and bypass some GUI issues.

  1. Place the Forge Installer JAR file on your Desktop or in another easy-to-access location.
  2. Open Terminal and navigate to that directory: 
    cd ~/Desktop
  3. Run: 
    java -jar forge-installer.jar

    Replace forge-installer.jar with the actual name of your file if different.

If the installer launches this way, the problem likely lies with Java’s GUI integration on macOS or file associations.

4. Associate .JAR Files with Java

If macOS doesn’t recognize .jar as a file type to open with Java, it might try to use Archive Utility or another unhelpful app. Fix this using these steps:

  1. Right-click the Forge installer JAR file.
  2. Click Get Info.
  3. Under Open with:, choose JavaLauncher or Jar Launcher if available.
  4. Click Change All to apply it to all JAR files.

If JavaLauncher isn’t listed, you may need to reinstall Java 8 or use a third-party app like Jar Launcher from an older macOS version.

5. Check for File Corruption

Sometimes, the Forge installer file doesn’t download properly, especially on slower connections or if interrupted midway.

  1. Try downloading the file again from the official Minecraft Forge website.
  2. Make sure you’re downloading the Installer and not the Universal or MDK files.

Some browsers like Safari may also auto-extract or rename files. Use Chrome or Firefox if you suspect the download is being modified.

6. Disable Gatekeeper Temporarily

Apple’s Gatekeeper prevents applications from unidentified developers from opening. Forge fits this description. You can temporarily override it:

  1. Go to System Settings > Privacy & Security.
  2. Scroll to the bottom where it says “App was blocked from opening” and click Allow Anyway.
  3. Then, right-click the JAR file and choose Open.

If the installer still doesn’t open, you can use Terminal to disable Gatekeeper:

sudo spctl --master-disable

Be cautious: This disables some system protections. Re-enable Gatekeeper afterward with:

sudo spctl --master-enable

7. Use an Older Version of Forge

Some newer versions of Forge may have compatibility issues with certain Java versions or macOS updates. Try using an older version (e.g., 1.16.5 or 1.12.2) and see if it works better.

This is also a great way to check whether the issue is with the installer itself or your environment.

Preventing Future Issues

To avoid this problem cropping up again:

  • Install multiple versions of Java using tools like SDKMAN.
  • Keep a version-specific Java folder and use scripts to launch JARs with the right version.
  • Avoid moving the Forge JAR into system folders like Applications or Library — keep it somewhere accessible like the Desktop.

Alternative Approach: MultiMC or PrismLauncher

If everything fails, consider using a third-party launcher like MultiMC or PrismLauncher. These launchers simplify the modding process and handle Forge integration automatically.

These tools allow easy profile creation, built-in Forge installation, Java version management, and more — offering a smoother modding experience.

Final Thoughts

Modding Minecraft on macOS with Forge can be a fun and rewarding experience — once the installation hurdle is overcome. Whether it’s due to macOS security, incompatible Java versions, or corrupted downloads, the issue of the Forge Installer not launching is thankfully fixable.

By following the step-by-step solutions outlined above, you’ll have Forge installed and working in no time. Happy modding!