There are many tools that help with quality assurance in OpenStreetMap and they come in many flavours. One popular class of these tools are web sites showing the OSM map in the background and (usually switchable) overlays with markers for different types of problematic OSM data. They usually allow you to jump directly into the OSM editors to fix the problems. The most prominent of these tools are Osmose, the OpenStreetMap Inspector, and KeepRight. But there are many more of these, often written for very specific use cases. All of these tools have the drawback that they are “closed systems”: The person developing the tool and/or running the web service decides which layers there are. The creation of those layers is often tied more or less closely to the tool showing the layers. At the recent Karlsruhe hack weekend I released a new tool, Osmoscope, of that same class, but with much more openness built in.