Abstract. SWiM is a semantic wiki for collaboratively building, editing and browsing mathematical knowledge represented in the domainspecific structural semantic markup language OMDoc. It motivates users to contribute to collections of mathematical knowledge by instantly sharing the benefits of knowledge-powered services with them. SWiM is currently being used for authoring content dictionaries, i. e. collections of uniquely identified mathematical symbols, and prepared for managing a large-scale proof formalisation effort.