Does CodeIgniter provide a Debug Mode, for example, when accessing an Invalid URL? Ruby on Rails does show debugging Messages when a incorrect URL has been given, and the controller is unable to resolve it using the routes map. How would I enable such debugging messages in CodeIgniter? The profiler ... $this->output->enable_profiler(TRUE); ... only affects single classes, but not all routes. So debugging without an actual debugger mode is a little... difficult. :-)