| io.reactivex | Base reactive classes: Flowable, Observable, Single and Completable; base reactive consumers; other common base interfaces. |
| io.reactivex.annotations | Annotations for indicating experimental and beta operators, classes, methods, types or fields. |
| io.reactivex.disposables | Default implementations for Disposable-based resource management (Disposable container types) and utility classes to construct Disposables from callbacks and other types. |
| io.reactivex.exceptions | Exception handling utilities, safe subscriber exception classes, lifecycle exception classes. |
| io.reactivex.flowables | Classes supporting the Flowable base reactive class: connectable and grouped flowables. |
| io.reactivex.functions | Functional interfaces of functions and actions of arity 0 to 9 and related utility classes. |
| io.reactivex.observables | Classes supporting the Observable base reactive class: connectable and grouped observables. |
| io.reactivex.observers | Default wrappers and implementations for Observer-based consumer classes and interfaces; utility classes for creating them from callbacks. |
| io.reactivex.parallel | Base type for the parallel type offering a sub-DSL for working with Flowable items in parallel. |
| io.reactivex.plugins | Callback types and a central plugin handler class to hook into the lifecycle of the base reactive types and schedulers. |
| io.reactivex.processors | Classes extending the Flowable base reactive class and implementing the Subscriber interface at the same time (aka hot Flowables). |
| io.reactivex.schedulers | Scheduler implementations, value+time record class and the standard factory class to return standard RxJava schedulers or wrap any Executor-based (thread pool) instances. |
| io.reactivex.subjects | Classes extending the Observable base reactive class and implementing the Observer interface at the same time (aka hot Observables). |
| io.reactivex.subscribers | Default wrappers and implementations for Subscriber-based consumer classes and interfaces; utility classes for creating them from callbacks. |