For a Piwik website or globally, it is already possible to exclude / ignore URL parameters. However, because the default request method is GET, ignored URL parameters would be still visible in the access log of the Piwik server.

Instead it would be great to be able to have a method in the JS tracker to ignore URL parameters like _paq.push(['setIgnoreUrlParams', 'sid', 'cid']);. Not sure what a good method name would be.

Because Piwik knows server side which parameters to ignore, we could also re-use this information in the JavaScript tracking code generator and automatically set this parameter.

In the tracker itself we already have a method removeUrlParameter() to remove a URL parameter so it should be not too hard to develop. We would add this probably to the method purify(url) where we already modify the URL based on configuration.