Abstract: Stack Overflow relies on the crowd to construct quality developer-related knowledge. What developers use the crowd constructed knowledge on Stack Overflow for is an open question. We answer this question, by analyzing 1,414 Stack Overflow related commits and observe that developers use this crowd based knowledge to support development tasks and to collect user feedback. We also studied the helpfulness and delay of Stack Overflow posts by identifying the type of questions that are more likely to be answered by the crowd. We find that development tools and programming language issues are areas where the crowd is most helpful and that web framework related issues are the most time consuming questions to receive an accepted answer for. Our findings can help developers better understand how to effectively use Stack Overflow as a development support tool, help Stack Overflow designers to improve their platform, and the research community to understand the strengths and weaknesses of Stack Overflow as a development tool.