Java support in Firefox has changed over the years due to security concerns. Modern versions of Firefox no longer support Java applets natively, but there are still ways to enable Java functionality in specific use cases. This guide explains three methods to enable Java in Firefox.

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Method 1: Use an Older Version of Firefox with NPAPI Support

Modern Firefox versions do not support NPAPI plugins, including Java. However, older versions such as Firefox 52 ESR (Extended Support Release) still support Java.

Steps to Enable Java on Firefox 52 ESR:

  1. Download Firefox 52 ESR from the Mozilla FTP Archive.
  2. Install the downloaded version and disable automatic updates.
  3. Install Java Runtime Environment (JRE) from Oracle’s website.
  4. Open Firefox and enter about:config in the address bar.
  5. Search for plugin.load_flash_only and set it to false.
  6. Restart Firefox and test Java functionality on Java Test Page.

Limitations:

  • Security risks due to outdated browser and plugin support.
  • May not be compatible with some modern websites.

Method 2: Use a Java Web Start (JNLP) Application

Even without NPAPI support, Java Web Start allows running Java applications from a browser by launching them externally.

Steps to Use Java Web Start in Firefox:

  1. Install the Java Runtime Environment (JRE).
  2. Ensure javaws.exe (Java Web Start) is associated with .jnlp files.
  3. Open Firefox and navigate to a website that provides a .jnlp file.
  4. Download the .jnlp file and open it with Java Web Start.
  5. The Java application will run outside the browser in a separate window.

Advantages:

  • More secure than using an outdated browser version.
  • Works on modern Firefox versions.

Method 3: Use an Alternative Java-Compatible Browser

Some browsers still support Java or provide better compatibility with Java-based applications.

Recommended Browsers:

  • Internet Explorer (IE 11): Still supports Java but is being phased out.
  • Pale Moon: A Firefox-based browser that may work with Java plugins.
  • OpenJDK + IcedTea-Web Plugin: Works on Linux systems for Java applets.

Steps to Use Internet Explorer for Java:

  1. Open Internet Explorer.
  2. Visit Java.com to verify Java installation.
  3. Allow Java to run when prompted.

Considerations:

  • Internet Explorer is deprecated and not recommended for security reasons.
  • Pale Moon and IcedTea-Web work mainly for legacy Java applications.

Conclusion

Since modern Firefox versions no longer support Java, the best alternatives are:

  • Using Firefox 52 ESR for NPAPI support.
  • Running Java Web Start applications.
  • Using a Java-compatible browser like Internet Explorer or Pale Moon.