TopBT (originally called Top-BT), is a topology-aware BitTorrent client. The "Top" in its name stands for "Topology". Compared with current widely-used BitTorrent clients, such as Vuze (previously known as Azureus), BitTorrent, and uTorrent, the unique feature of TopBT is, it actively discovers its network proximities to its connected peers. It does so by actively sending packets to those peers, and inspecting their responses. In addition to the merits of topology-awareness, TopBT also attempts to improve network Transmission rates to its peers, so that it can download fast.

TopBT aims to achieve two main goals. First, to reduce unnecessary network traffic due to topology-unawareness. This is an important task in Internet management, because BitTorrent traffic accounts for more than 40% of total Internet traffic as reported in an IPOQUE report in 2007. Second, to maintain fast download speed: a comparable download speed to that of existing and efficient BitTorrent clients on average will be maintained, if not faster than them.

TopBT has been implemented with open-source Vuze code base Version 4.0.0.4. Our evaluation results from typical runs on Windows XP show that TopBT can achieve comparable download speed compared to that of Vuze and uTorrent, sometimes even faster. More importantly, it can save Internet traffic significantly, often cutting hundreds of mega bytes of traffic for a downloading file of Giga bytes.