The Realtime library is most commonly used client-side and is stateful, it establishes a connection to Ably for that client and maintains state for the life of the connection. Reasons to use the Realtime library are:

  • You are developing a mobile, desktop or web client that needs to subscribe to messages in real time.
  • You want to maintain a persistent connection to Ably, attach to one or more channels, and publish and subscribe to messages.
  • Your application needs to register its presence on a channel, or listen for others becoming present in real time.


The REST client library is most commonly used server-side i.e. on your application servers, and is stateless. Reasons to use the REST library are:

  • Your application server is used to primarily issues tokens for clients and/or publish messages on channels.
  • Your application is mostly stateless i.e. you process a request or respond to an event, and then move onto the next request or event without any previous state carrying through.
  • Your prefer a synchronous request over an asynchronous request. Note not all REST libraries are synchronous, but where the platform offers a synchronous and asynchronous approach, the REST libraries are more often synchronous.


Other libraries and supported protocols to consider


For more information, please see the Realtime usage documentation.