Average mobile app loses >70% of its users in 3 days. Within 30 days >90% of users are lost. Are you below or above the benchmark? What's your D1/D3/D7/D30 retention? This talk will focus on retention metric, why you should track it and how can you track it. We'll see how retention influences acquisition, monetization, and LTV through a series of industry-backed examples. At the end, we'll have a look at some of the techniques which app developers use to boost retention and fix that leaky bucket.