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 optimal use cases for each channel type can vary as different channels support different features. The following tables compare open channels, group channels, and Supergroup channels in terms of possible use cases and supported features.

Choose which channel type to use based on key factors such as the duration of a chat and the number of users participating in it. The following table lists possible use cases for each channel type.

The following table compares the difference among three types of channels.