SD is a peer-to-peer (P2P) bug tracking system that allows users to track bugs and work even when offline or without reliable network access. It was created by Jesse Vincent, the founder of Best Practical, because existing bug tracking solutions did not meet his needs as someone who spends a lot of time traveling without reliable WiFi access. SD synchronizes issues and changes across devices and other issue trackers using a distributed model rather than depending on a centralized network infrastructure.