 OK, let's take it back, right back to the 1820s. And this is Babbage's Difference Engine. It was designed to tabulate polynomial functions, such as logarithms. One machine, one app, hand-built, hard-coded. To get a new app, you had to get Babbage to design a new machine. And, well, as it happened, wait nearly two centuries for someone to actually build it. Now, move forward 150 years, and software looked like this. Big programs needed 10 or more floppy disks. Compact disks, and later DVDs, were a revolution. The MapPoint app, for example, could be bought from a bookstore. This had pan and zoom, and it completely changed trip planning. Web-based maps at the time couldn't do anything like that. Well, let's move forward a few years. Google Maps happened. And this worked on any computer, not just one that you'd spent 30 minutes installing on. Google Maps showed that the web's distribution model can really work. However, on mobile, well, we've seen something different. Now, raise your hand if you use Google Maps on the web on desktop. But what about on mobile? Do you open a browser to use Google Maps on a phone? I'd guess not many of you. So the hardest problem with software is distribution. And anyone who's ever worked in IT will understand this. So how does this play out on mobile? Well, it's true that users spend most of their time in native apps. Re-engagement features keep users in apps. Notifications bring users back, even when the app is closed. And home screen icons maintain visibility. But usage is highly concentrated. It's a winner-take-all situation. App developers often spend more for distribution than they actually earn back. So if the native ecosystem isn't going so well, why hasn't the web been even more disruptive? Well, here's one way to think of the differences between web and native, the capability access. Native apps have the ability to start up fast and reliably. They can work offline and use push, sync, sensors, and so on. Now, the web has been perceived as safer and more respectful of privacy, but it doesn't have those native features. If we add another access, reach, you can see where the web succeeds. Google data shows that mobile users visit around 100 sites per month. This is the power of URLs. They meet one-off needs. But what if the web could meet those user expectations? This is what progressive web apps represent, PWA for short. Web apps are finally able to earn their place on the home screen and in the notification tray. And they don't have to give up on reach. So what was missing from the web? Well, first we needed reliability and performance on par with native apps. Next, we needed to be in the notification tray. And lastly, for trustworthy apps, we needed to be on the home screen. So now let's talk about performance. We all know time is money, and this data shows just how badly bounce rate increases with load time. Other studies show that after just three seconds, 40% of users will abandon a website. 40%. But what if you didn't need to traverse the network every time for every asset? What if you could intelligently cache assets locally, reliably? Well, that's what service workers do. Service workers enable you to implement caching with the Cache API, not just by hoping to rely on browser caching. This means that after the first visit, sites and apps can be reliably fast. Well, that's huge, but what about the first visit? The AMP project from the Google search team was built to address the web obesity epidemic. AMP provides reliably fast web components for first load. These AMP components can be much faster to load and less data hungry than non-AMP content. Well, what if you could combine the two, fast first load with reliable performance subsequently? Well, we can do that by combining AMP and service worker. You know, this is where AMP meets PWA. So do you want to try out progressive web apps? Well, there are great tools built into the Chrome Dev tools. For PWA developers, Google engineers have created Lighthouse. This reports on how well your site or app is doing in terms of performance, security, accessibility, SEO, and PWA features. You also get command line tools you can build into your workflow and production processes. So to sum up, PWAs are reliable, fast, and engaging. You know, we've been really excited to see incredible momentum across the globe. Here's a sample of folks shipping or actively working on PWAs and new web APIs. With these early adopters, we've seen that every site has their own way of investing in mobile web and starting down the path towards progressive web apps. So now it's your turn. Thanks for watching.