What are Log Files?


Log files are simple text files maintained by web servers and containing a record of downloads of web pages and other files. When a web browse requests a page from a web server, such as the web server looking after www.oii.ox.ac.uk, it can add a new line to the end of the log file with information such as the URL of the requested page, the IP address sending the request, and the date and time of the request. Since a web page is typically made up of several files, including the main HTML and embedded images, a request for a web page may result in many lines being added to the web server log file, one for each individual file sent.

Here is the official computer science description of the contents of each line of a common log file, taken from the official source. Some of the information is more technical or only used for secure areas of a website that are password-protected.

The common logfile format is as follows:

    remotehost rfc931 authuser [date] "request" status bytes remotehost

Remote hostname (or IP number if DNS hostname is not available, or if DNSLookup is Off.


The remote logname of the user.


The username as which the user has authenticated himself.


Date and time of the request.


The request line exactly as it came from the client.


The HTTP status code returned to the client.


The content-length of the document transferred.


Taken from: www.w3.org/Daemon/User/Config/Logging.html


The precise information saved in any line of a log file depends upon the web server used and the settings of the web server, as configured by its administrator. If there is not enough information in your web server log files then the first step would be to ask the administrator whether it is possible to change the configuration of the web server to add in the necessary additional information.