Imagine a situation where your services report healthy and serving but you receive multiple user reports of poor availability. How are these users accessing your service? Most likely, they are using your service through a client application, such as a mobile application on their phone. SRE traditionally has only supported systems and services run in datacenters rather than the code running on the client, and this can lead to issues that go unnoticed until it is too late. This report explains the importance of client-side reliability, describes the challenges of working in such an environment, and provides a useful set of SRE concepts and potential tools to apply to your own client applications.