What is the default.filter file? What is a “filter”?
The default.filter file is where filters as supplied by the developers are defined. Filters are a special subset of actions that can be used to modify or remove web page content or headers on the fly. Content filters can be applied to anything in the page source, header filters can be applied to either server or client headers. Regular expressions are used to accomplish this. There are a number of pre-defined filters to deal with common annoyances. The filters are only defined here, to invoke them, you need to use the filter action in one of the actions files. Content filtering is automatically disabled for inappropriate MIME types, but if you now better than Privoxy what should or should not be filtered you can filter any content you like. Filters should not be confused with blocks, which is a completely different action, and is more typically used to block ads and unwanted sites. If you are familiar with regular expressions, and HTML, you can look at the provided default.
