The Twitter Monitor is an interactive Web application designed to access the Twitter stream by exploiting the public Twitter Streaming APIs. The application can manage concurrent monitors, so it is possible to launch parallel listening sessions (i.e., more than one Twitter crawler at the same time) using different parameters and collecting different sets of data. It is equipped with an interactive Web interface in order to ease all the operations related to Twitter crawling, and it offers a set of functionalities aimed at minimizing the loss of data due to network or local machine issues.