How to Fix Java Applet Security Errors

Security Errors When Loading Java Applets?

Did you get errors like the following when you tried to run a Java applet in the web browser?

Application Blocked
Your security settings have blocked an untrusted application from running.

For security reasons, recent versions of Java may block unsigned Java applets from automatically running by default.

Solution

If you trust the unsigned Java applet to be safe, you can workaround this problem by adding an "Exception Site":

For Microsoft Windows:

  1. Click on the Windows "Start" menu in the lower-left corner of the screen --> "Control Panel" --> "Programs" --> "Java".
  2. In the "Java Control Panel" window that appears --> Click the "Security" tab.
  3. In the "Exception Site List" section in this window, click on the "Edit Site List..." button --> Click the "Add" button --> Type in the web server location for the Java applet like "http://www.math.ucsd.edu/" --> Click the "OK" button --> Click the "OK" button.
  4. Close ALL of the open windows. Then QUIT the web browser. You must completely QUIT the web browser or this workaround will fail.
  5. Re-launch the web browser.
  6. Go to the Java applet.
  7. When the "Security Warning" window asking "Do you want to run this application?" appears --> Click the "Run" button.
  8. The Java applet should load OK now. You may need to click on it to start it.
  9. When you are done using the Java applet, you should remove the Exception Site entry from the Java control panel if it is no longer needed.

For Mac OS X:

  1. Click the "Apple" menu in the upper-left corner of the screen --> "System Preferences..." --> "Java".
  2. In the "Java Control Panel" window that appears --> Click the "Security" tab.
  3. In the "Exception Site List" section in this window, click the "Edit Site List..." button --> Click the "Add" button --> Type in the web server location for the Java applet like "http://www.math.ucsd.edu/" --> Click the "OK" button --> Click the "OK" button.
  4. Close ALL of the open windows. Then QUIT the web browser. You must completely QUIT the web browser or this workaround will fail.
  5. Re-launch the web browser.
  6. Go to the Java applet.
  7. When the "Security Warning" window asking "Do you want to run this application?" appears --> Click the "Run" button.
  8. The Java applet should load OK now. You may need to click on it to start it.
  9. When you are done using the Java applet, you should remove the Exception Site entry from the Java control panel if it is no longer needed.

References