The popularity of web-based services and appli- cations like YouTube and Facebook has taken HTTP back to the pole position on end-user traffic consumption. We present HTTPTag, a flexible on-line HTTP classification system based on pattern matching and tagging. HTTPTag recognizes and tracks the evolution of more than 280 HTTP applications on the fly. This applications are responsible for about 70% of the HTTP traffic in the investigated operational 3G network. HTTPTag improves the network traffic visibility of an operator, performing tasks such as top-services ranking, long-term monitoring of the application popularity, and trend analysis among others.