What if we built our digital libraries for the preservation moment? What if they were portable, worked offline, and could be emulated in any web browser? Emerging Web application architectures utilizing offline modes, cacheing of data, and packaged Web software are becoming widely supported. These Progressive Web Apps (PWA) have tremendous value for our repository architectures. PWAs use advances in offline storage, metadata manifest files, and Javascript functionality to store data and create software interfaces that act/perform like native device applications. More importantly, PWAs use the most ubiquitous, open technology platform, the Web, as their means for distribution and display. They allow us to create once and publish everywhere. In this session, we'll consider the common PWA models as well as the implications these models have for digital library design, software architectures, archiving routines, and metadata. We'll look at how PWA methods can be applied to a digital library by grounding our work in an implementation. Our case study will be the James Willard Schultz Collection, a digital library application rewritten as a PWA (GitHub repo). Our goal will be to understand the PWA development model and why PWAs will help the "archiveability" and emulation of our digital libraries.