Google has announced the Firebase App Indexing API which enables apps to add content to Google's on-device index. The API is similar in functionality to the search mode, which is called In Apps, that Firebase announced earlier this year. However, instead of installing apps such as OpenTable, Ticketmaster, Evernote, or others in order to find content within such apps; the App Indexing API allows all Android developers access to such functionality. Users can directly navigate to content searched directly within an app from a Google search box. For apps not yet installed, relevant searches trigger an install recommendation.
The goal of the API is to increase user engagement with an integrated app. Users can retrieve personal content with a Google search. Developers maintain full control over the content type that goes into the index, and how/when such content is indexed. Since the data remains on the device, users have access to such content on and offline.
The API contains multiple predefined data types (i.e. messages, notes, songs, and custom types). The data types allow developers to easily represent common content types for indexing. Firebase logs user interaction with such types to better rank user content across the Google app. The API updates in real-time in the background as users change and update an app.
Key functionality includes search results, installs, autocompletions, Google Assistant, and ad targeting. Google has included a number of real-world App Indexing examples from Cookpad, Etsy, The Guardian, and others in its Implementation Guide. To learn more, visit the API docs or get started on codelabs.