Squid has some very detailed logging options which can be activated in this area.
Log enable = By activating this option, the web-proxy logging is enabled. The logs can be viewed under /logs/proxy logs over the WUI, or via the console under the path/var/log/squid. If needed, you can find even more information about the logs in here . In the wiki section "Logs" there are also statements regarding to the proxy logging which can be found in Proxy-Logs and Proxy-Summary.
Log query terms: = Query data (query-terms) or dynamic content of an URL aren´t logged by default by Squid because of data privacy protection reasons, since query terms can also include e.g. passwords . If this option is activated, the full URL will be logged.
Example with query term logging:
1326376573.979 172 192.168.205.2 TCP_MISS/200 3605 GET http://wiki.ipfire.org/de/configuration/network/proxy? do=login§ok=898d87a4cdeed875a0fa3e3254fgh0bf user DIRECT/188.8.131.52 text/html
Example without query term logging:
1326376486.158 122 192.168.205.2 TCP_MISS/200 3605 GET http://wiki.ipfire.org/de/configuration/network/proxy? user DIRECT/184.108.40.206 text/html
Log useragents = With enabled option, the data of the user agent field in the header of the requests will be written into the file/var/log/squid/useragent.log. This logging option collects data about the browser and the operating system from the clients.
An example for useragent logging:
192.168.23.5 [08/Jan/2012:15:50:17 +0100] "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0.1) Gecko/20100101 Firefox/8.0.1"