Tracing and Logging

Tracing and Logging includes the following topics:


Tracing is a facility to redirect any output in the Java Console to a trace file.

Java Plug-in

Tracing can be turned on by enabling the property javaplugin.trace. However, it turns on all tracing facilities inside Java Plug-in. To enable more fine-grained tracing, javaplugin.trace.option may be used. You can set trace-level options (0-5) in the Java Console, shown in the previous chapter, with the following meanings:

This enables tracing on the fly.

Another way to set fine-grained tracing is through the Java Control Panel. For instance, to enable tracing for everthing (option 5 above), enter the following in the "Java Run Time Parameters" textfield:


Tracing set through the Control Panel will take effect when the Plug-in is launched, but changes made through the Control Panel while a Plug-in is running will have no effect until restart.

Java Web Start

To set the initial trace level for a Java Web Start application, you can create a .javawsrc file in either your home directory or the jre/bin directory. This file can have entries:



Similar to tracing, logging is a facility to redirect any output in the Java Console to a log file using the Java Logging API. Logging can be turned on by enabling the property javaplugin.logging:


Other Options

File Names

By default the trace and log file names are, respectively:

.plugin<version>.trace and .plugin<version>.log

However, you can give them different names by setting the properties:

javaplugin.trace.filename and javaplugin.log.filename

in the Java Plug-in Control Panel.

File Location

The default location (directory) of Java Plug-in related files is:

However, the location can be set with the environment variable USER_JPI_PROFILE.

Overwrite Option

Furthermore, if you do not want to overwrite trace and log files each session, you can set the property javaplugin.outputfiles.overwrite=false. If the property is set false, then trace and log files will be uniquely named for each session. E.g., if default trace and log file names are used as shown above, then date information would be included as follows:

.plugin<username><date hash code>.trace and .plugin<username><date hash code>.log