After upgrading to macOS Big Sur I couldn't run Oracle SQL Developer. I got the following error: The application “SQLDeveloper.app” can’t be opened

{% asset_img macos-error.png %}

To resolve this issue I got help from Kris Rice and Niels de Bruijn. The issue is caused by Apple and the Java applet plugin.

Here's how I got SQL Developer working:

List your Java Versions

/usr/libexec/java_home -V

# This will give an output like:

Matching Java Virtual Machines (3):
    11.0.2 (x86_64) "Oracle Corporation" - "Java SE 11.0.2" /Library/Java/JavaVirtualMachines/jdk-11.0.2.jdk/Contents/Home
    1.8.271.09 (x86_64) "Oracle Corporation" - "Java" /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home
    1.8.0_201 (x86_64) "Oracle Corporation" - "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home
/Library/Java/JavaVirtualMachines/jdk-11.0.2.jdk/Contents/Home

The one that caused the problem is the "Oracle Corporation" - "Java" /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home and you'll need to remove it.

Remove the Applet Plugin

sudo rm -rf "/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/"


# After deleting this folder it should be removed from the Java Home list
/usr/libexec/java_home -V

# Output
Matching Java Virtual Machines (2):
    11.0.2 (x86_64) "Oracle Corporation" - "Java SE 11.0.2" /Library/Java/JavaVirtualMachines/jdk-11.0.2.jdk/Contents/Home
    1.8.0_201 (x86_64) "Oracle Corporation" - "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home
/Library/Java/JavaVirtualMachines/jdk-11.0.2.jdk/Contents/Home

If you run SQL Developer now it should work. I'm not sure about the side effects of removing this Java applet plugin. If I find it to be critical to other things I'll be sure to update this post.