Log files are your main source for problem diagnostics and various squid operations.
There are cache.log, access.log, and store.log. You can find them in /var/log/squid directory.
The cache.log file contains informational messages about Squid’s operation. All proxy errors are written to this file.
The access.log file contains all HTTP request made by the clients.
The store.log file contains information about the passed objects.
Each entry on these files is written with time stamps when the message was generated.