Google has sent their newest APK packaging format for Android, WebAPK, out into the world in the form of a test page left sitting around in a Google forum thread by a developer. WebAPK is meant to merge web apps and native Android apps, and boasts a few unique advantages of its own. The test page and app in question don't do much, aside from showing how WebAPK works as a standard, and how users could go about getting new apps. Known as "Long Train", this proof of concept installs a testing app called "Short Train" on the target device, so long as a few specific requirements are met on the host device.
When a user heads over to the test link in Chrome for Android, they are given a download link for Long Train. A visit on a non-mobile browser will net you a QR code for a phone to scan. Hitting this link brings you to the Install Wizard, with Short Train ready to install. Once it's installed, it will reside on your home screen, where you can use it to head back to the test page. Once installed, the app takes up only 20 kilobytes on a user's device, which seems about on target, given its fairly basic functionality.
Speculation pegs WebAPK as a standard for "progressive web apps", a type of web app that mimics a native app in user interface, and through the dual magics of caching and machine learning, becomes faster, more responsive, more feature-rich, and more powerful each time a user opens it up. In order to check out the WebAPK test for yourself, you'll need to be using a version of Chrome besides the stable one, and enable the right flags through Chrome://flags. The correct flag does reportedly exist in vanilla Chrome, but the flag does not seem to actually enable WebAPK functionality. Flipping the switch that adds the app to your homescreen automatically requires enabling the installation of software from sources outside of Google's Play Store. With a basic demo now in the wild and the functions for it already built into newer versions of Chrome, it likely won't be long before WebAPK is supported in an official capacity by Google as a protocol for combining the benefits of a web app and a native app.