FitNesse has two different types of logging: system logging and access logging.

!2 System logging
System logging is performed via ''java.util.logging''. This is the default logging facility bundled with Java. By default only messages with info level and up are logged. The -v option can enable more verbose logging by default. Logging is sent to stderr.

It's possible to fully customize the logging output, including redirecting it to files. In order to do so, one has to create a log configuration file in accordance to the properties available to the different handlers. See the API documentation for [[!-LogManager-!][http://docs.oracle.com/javase/7/docs/api/index.html?java/util/logging/LogManager.html]], [[!-ConsoleHandler-!][http://docs.oracle.com/javase/7/docs/api/index.html?java/util/logging/ConsoleHandler.html]] and [[!-FileHandler-!][http://docs.oracle.com/javase/7/docs/api/index.html?java/util/logging/FileHandler.html]] for some inspiration. FitNesse by default uses a custom log formatter: ''!-<i>fitnesse.logging.LogFormatter</i>-!''. This formatter provides some simple formatting and does only print log severity and exception stack traces for warning level and up.

The default log configuration looks like this:

{{{handlers = java.util.logging.ConsoleHandler
java.util.logging.ConsoleHandler.formatter = fitnesse.logging.LogFormatter}}}
!2 Access file

If File logging is turned on (with the -l command line argument) then FitNesse will record all accesses in log files.

A new log file is created every day.

Log files are named fitnesseyyyymmddhhmmss.log, where yyyymmddhhmmss is the time of the first log entry in the file.

Each line in the log file records a separate access.  They are written in standard (common) web log format.  They look like this:{{{
65.194.52.68 - - [06/Mar/2003:16:33:48 -0600] "GET /FitNesse.UserGuide HTTP/1.1" 200 1965
65.194.52.68 - - [06/Mar/2003:16:33:49 -0600] "GET /files/images/FitNesseLogoIcon.jpg HTTP/1.1" 200 15026
65.194.52.68 - - [06/Mar/2003:16:33:54 -0600] "GET /files HTTP/1.1" 404 380
65.194.52.68 - - [06/Mar/2003:16:34:00 -0600] "GET /files/ HTTP/1.1" 200 650
65.194.52.68 - - [06/Mar/2003:16:34:00 -0600] "GET /files/images/FitNesseLogoIcon.jpg HTTP/1.1" 200 15026
65.194.52.68 - - [06/Mar/2003:16:34:04 -0600] "GET /files/logs/ HTTP/1.1" 200 414
65.194.52.68 - - [06/Mar/2003:16:34:04 -0600] "GET /files/images/FitNesseLogoIcon.jpg HTTP/1.1" 200 15026
65.194.52.68 - - [06/Mar/2003:16:34:05 -0600] "GET /files/logs/fitnesse20030306163348.log HTTP/1.1" 200 650
}}}