EnhancedPatternLayout is the log4j 1.3 pattern layout backported to log4j 1.2 and has been in the extras companion for several years. Making this appender available in log4j.jar should be beneficial to those users would like to use it, but do not wish to add another jar to their classpath. EnhancedPatternLayout will continue to be available in the extras companion for use with earlier log4j's.