Facebook open sources at scale. This means that we have hundreds of projects and hundreds of engineers working to maintain those projects and keep healthy interactions with hundreds of thousands of community members. We've found that the key to a successful open source project is how the community is nurtured -from building initial trust to bringing in core external contributors. I will go through a few case studies from our projects and guide you through their adventures in building their communities. Tooling, responsiveness, empathy, patience, and transparency are some of the topics I will explore. You should come away with key best practices that you can apply in building your own thriving open source community.