All APIs for communicating with the Android system.

Build Realtime Apps. A powerful API to store and sync data in realtime.

Google Play services offers a standard authorization flow for all Google APIs and all components of Google Play services. In addition, you can leverage the authorization portion of the Google Play services SDK to gain authorization to services that are not yet supported in the Google Play services platform by using the access token to manually make API requests or using a client library provided by the service provider.

Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.

Make your games social with Google Play game services. Add achievements, leaderboards, real-time multiplayer, and other popular features using the Google Play game services SDK. Let players sign in using their Google+ identities and share their gaming experience with friends. Visit developers.google.com/games/services for more information about integrating game services into your app.

Google Play Services give your apps more features to attract users on a wider range of devices. With Google Play services, your app can take advantage of the latest, Google-powered features such as Maps, Google+, and more, with automatic platform updates distributed as an APK through the Google Play store. This makes it faster for your users to receive updates and easier for you to integrate the newest that Google has to offer.

The collection of search and search related APIs in Google's Android GMS framework.

Google Sign-In is a secure authentication system that reduces the burden of login for your users, by enabling them to sign in with their Google Account—the same account they already use with Gmail, Play, Google+, and other Google services. Google Sign-In is also your gateway to connecting with Google’s users and services in a secure manner. You can give your users the opportunity to pay with Google Pay, share with their Google-wide contacts, save a file to Drive, add an event to Calendar, and more. Integrate Google’s user-centric APIs and services inside your app to help your users take action and convert.

Okio is a new library that complements java.io and java.nio to make it much easier to access, store, and process your data.

HTTP is the way modern applications network. It’s how we exchange data & media. Doing HTTP efficiently makes your stuff load faster and saves bandwidth. OkHttp is an HTTP client that’s efficient by default: HTTP/2 support allows all requests to the same host to share a socket. Connection pooling reduces request latency (if HTTP/2 isn’t available). Transparent GZIP shrinks download sizes. Response caching avoids the network completely for repeat requests. OkHttp perseveres when the network is troublesome: it will silently recover from common connection problems. If your service has multiple IP addresses OkHttp will attempt alternate addresses if the first connect fails. This is necessary for IPv4+IPv6 and for services hosted in redundant data centers. OkHttp supports modern TLS features (TLS 1.3, ALPN, certificate pinning). It can be configured to fall back for broad connectivity. Using OkHttp is easy. Its request/response API is designed with fluent builders and immutability. It supports both synchronous blocking calls and async calls with callbacks.