Channel types

Sendbird's SDKs and API provide two basic types of channels. Each type is designed and implemented to support a wide variety of use cases that your business requires. This page presents the differences and characteristics of the two types.

An open channel is a public chat by nature that can handle a large number of online users. A single open channel can accommodate up to 1,000 simultaneous users in a Twitch-style public chat, and anyone can easily participate without permission. This maximum number of participants can increase per request.

• Ephemeral: Messages in an ephemeral open channel are not saved in Sendbird's database. This means that old messages pushed out by new ones can't be retrieved as they are one-time data. On the other hand, messages in a persistent open channel are permanently stored in the database, which is the default.

A group channel is a chat that allows close interactions among a limited number of users. In order to join this type of channel, an invitation from a channel member is required by default. Depending on how you implement the joining process in your application, a user who is invited to a group channel can accept or decline the invitation. However, various properties can be leveraged to design different types of group channels that suit your use cases, such as Twitter-style 1-on-1 direct messaging, WhatsApp-style group chat, and more.

• Public: A public group channel can be joined by any user without an invitation. Users can freely join the channel if they want to. On the other hand, a private group channel only accepts invited users by default.

• Distinct: The distinct option determines whether to resume an old channel or to create an entirely new one when someone attempts to open a new channel with a pre-existing member combination. If there is a group channel with those members, the attempt will re-start the existing channel that has their chat history. This is similar to Twitter-style 1-on-1 direct messaging and more. The default value is false.

• Supergroup: A Supergroup channel is an expanded version of a group channel, which can accommodate more than 2,000 members in one channel. The super option determine whether a newly created channel will be a Supergroup channel or a group channel. When this option is set to true, the distinct option can't be supported.

• Ephemeral: Messages in an ephemeral group channel are not saved in Sendbird's database. This means that old messages pushed out by new ones can't be retrieved as they are one-time data. On the other hand, messages in a persistent group channel are permanently stored in the database, which is the default.

The following table compares the difference among three types of channels that can accommodate a large number of users: Open channels, Group channels, and Supergroup channels.