GCViewer (download) is a free open source tool to visualize data produced by the Java VM options -verbose:gc and -Xloggc:<file>. It also calculates garbage collection related performance metrics (throughput, accumulated pauses, longest pause, etc.). This can be very useful when tuning the garbage collection of a particular application by changing generation sizes or setting the initial heap size. See here for a useful summary of garbage collection related JVM parameters. For more information on tuning garbage collection on Sun JVMs, take a look at the documentation provided by Oracle.

Supported Formats

Best results are achieved with: -Xloggc:<file> -XX:+PrintGCDetails

Data Export

GCViewer can also export the data in CSV (comma separated values) format, which may easily be imported into spreadsheet applications for further processing.

Contribute/Newer Versions

I have stopped improving GCViewer in 2008, however, there is a current fork by Jörg Wüthrich at https://github.com/chewiebug/GCViewer that aims at improving compatibility with current JVMs.


GCViewer has been developed with J2SE 1.4 and is licensed under LGPL.

The icons used were created and are copyrighted by Dean S. Jones, www.gallant.com/icons.htm

To find out more about how to use GCViewer, please read the article published in Jack Shirazi's performance newsletter.

Other GC related Tools and Links