In your Piwik Javascript Tracking tag, add the following line:

_paq.push(['setCustomUrl', location.href.toLowerCase()]);

just before the line:

_paq.push(['trackPageView']);

All your pages will now be tracked as lowercase, eg. “Default.aspx” or “DEFAULT.aspx” will be tracked as “default.aspx”.

If instead of the Javascript Tracker you are using the import_logs.py Log Analytics tool, then you can pass the following option to the import_logs.py script:

--force-lowercase-path