Read state and unread counts

Every channel and every thread keeps a read state for each of its members: when they last read it, and how many messages they haven't read since.

Channel lists, unread badges, unread separators and "jump to first unread" all build on this state. Channels and threads keep it in different shapes, so this page covers channels first, then threads.

Read state per user

A channel's read state is the read field of channel.state, one entry per user id:

The current user's count is also channel.state.unreadCount, and Channel.countUnread() returns the same. Both read the current value without subscribing. To follow it, subscribe to channel.state and select the current user's entry:

import { nsToDate } from "stream-chat";
import type { Channel } from "stream-chat";

export const followOwnReadState = (channel: Channel) => {
  const ownUserId = channel.getClient().userId;

  return channel.state.subscribeWithSelector(
    ({ read }) => ({ ownRead: ownUserId ? read[ownUserId] : undefined }),
    ({ ownRead }) => {
      if (!ownRead) return;
      const lastRead = nsToDate(ownRead.last_read).toLocaleString();
      console.log(`${ownRead.unread_messages} unread since ${lastRead}`);
    },
  );
};

Timestamps are nanosecond numbers. nsToDate turns them into a Date, as Data conventions explains. In a component, select read with useStateStore, as the unread badge on Reading state in components does.

A few more reads:

• Channel.lastRead() is the current user's last_read, or null if they never read the channel.
• Channel.countUnread(lastRead) counts the loaded newest messages after lastRead that count as unread.
• Channel.countUnreadMentions() counts the unread messages that mention the current user.

What changes the read state

• The state changes on its own, through events. That includes changes the user makes on another device.
• Other members' entries in channel.state.read update too. When someone posts, their entry becomes read and everyone else's count goes up. Read receipts depend on this.
• Channels the client doesn't watch still get the user's own read changes. They don't get other members' read changes.
• The server's count wins. The client's count is an estimate, and each time the channel loads, the server's count replaces it.

Each event changes it this way:

A message the current user sends, a reply that stays in its thread, and message.read or notification.mark_read for a thread don't change the channel's read state.

message.read_locally carries the newest loaded message as last_read_message_id only while the newest messages are loaded. When only an older interval is loaded, for example after a jump, the event carries none, and the read covers everything up to the event's time.

What counts as unread in a channel

When a new message arrives in a channel, it raises the current user's count unless:

• the current user sent it;
• it's silent (silent: true) or shadowed by moderation;
• it's a thread reply that isn't shown in the channel;
• the current user muted its author;
• the current user muted the channel;
• the user is looking at the newest messages, as Message paginators explains;
• the user doesn't have the read-events capability in the channel, unless the app counts unread messages locally (see Turning read events off).

The SDK's message lists report that the user is looking at the newest messages while the app is in the foreground and the newest message is on screen.

Channel.countUnread(lastRead) and Channel.countUnreadMentions() follow the same rules, except the one about looking at the newest messages.

Marking read and unread

Marking read or unread usually sends a request, and the read state changes when the server's event comes back, not when the call returns. Marking read locally changes it at once.

• Channel.markReadViaReporter() marks the channel read the way the SDK does on its own, through client.messageDeliveryReporter. It calls your markReadRequest handler if you registered one, resets the count locally when read events are off and local counting is on, and calls Channel.markRead() otherwise. Use it when your UI marks a channel read.
• Channel.markRead() always sends the request, even when you registered a handler. With { message_id }, it marks the channel read up to that message. Use it inside a markReadRequest handler. It throws unless the channel is loaded, or restored from the offline database, and read events are on.
• Channel.markReadLocally() resets the current user's count without a request, for channels whose unread messages are only counted locally.
• Channel.markUnread({ message_id }) marks the channel unread from that message. It takes message_timestamp instead of message_id too. Like Channel.markRead(), it throws when the channel isn't loaded or read events are off.

await channel.markUnread({ message_id: messageId });
// read[ownUserId].first_unread_message_id is set when notification.mark_unread arrives

To change how the SDK marks a channel read, register a markReadRequest handler. Channel.markReadViaReporter() and the SDK's own marking use it. The handler receives the channel and the options, and returns the response, or null when it sent nothing:

client.config.set({
  channel: {
    requestHandlers: {
      markReadRequest: async ({ channel, options }) => {
        // Livestream channels are never marked read.
        if (channel.type === "livestream") return null;
        return await channel.markRead(options);
      },
    },
  },
});

Message operations explains request handlers. What's optimistic and what isn't lists when each read action shows.

When the SDK marks a channel read

stream-chat doesn't mark a channel read by itself. The SDK's components do, at these moments:

• <Channel> mounts. When the current user had unread messages in the channel as it mounted, <Channel> marks it read once the channel has loaded. The list keeps showing where the unread messages start. Pass markReadOnMount={false} to leave the read state alone.
• A message arrives while the user is at the newest messages. The channel's message list marks the channel read when a new message arrives while the app is in the foreground and the newest message is on screen, unless the user marked the channel unread.
• The user goes to the newest messages. Pressing the scroll-to-bottom button in a channel, or closing the unread messages notification, marks the channel read.
• The connection recovers. When connection.recovered arrives and the channel's list is at the newest messages, <Channel> marks it read. A list that shows an older interval, with the newest messages not loaded, is left alone. Connection explains the event.

Each time, the SDK goes through client.messageDeliveryReporter, which uses your markReadRequest handler and sends at most one request a second per channel. When read events are off, it calls Channel.markReadLocally() instead, but only with localUnreadCountEnabled on (see below), and otherwise does nothing. The markReadRequest handler isn't called then.

A thread list doesn't mark the channel read. <Thread> activates its thread, and an active thread marks itself read, as Read state in threads explains.

useMarkRead(channel) returns the function the SDK uses, for a component of your own that should mark the channel read the same way. By default it also clears the list's unread boundary, so the unread separator and the unread notification go away. Pass { updateChannelUnreadState: false } to keep them:

import { Pressable, Text } from "react-native";
import { useChannel, useMarkRead } from "stream-chat-react-native";

export const MarkReadButton = () => {
  const channel = useChannel();
  const markRead = useMarkRead(channel);

  return (
    <Pressable accessibilityRole="button" onPress={() => markRead()}>
      <Text>Mark as read</Text>
    </Pressable>
  );
};

Turning read events off

To turn read events off, turn off the channel type's read_events setting on the server. The user can then no longer mark the channel read, and nothing counts unread messages.

readEvents.enabled: false in client.config does less. It only stops this client from marking channels read, and Channel.markRead() and Channel.markUnread() throw. The server and the client still count unread messages, so the user's count keeps going up. The client counts in channels where the current user has the read-events capability, which the server derives from the channel type, and the client setting doesn't remove it. Use it for a client that shouldn't mark anything read, such as a moderation tool:

client.config.set({ channel: { readEvents: { enabled: false } } });

channel.config.readEvents.enabled is false when the channel type's read_events is off on the server, or readEvents.enabled is false in client.config.

A livestream channel type usually has read_events off on the server, so nothing counts unread messages. To count them anyway, turn on localUnreadCountEnabled. The client then counts new messages itself, and Channel.markReadLocally() resets the count. While read events are off, Channel.markReadViaReporter() and the SDK's own marking call it for you:

client.config.set({
  channel: { readEvents: { localUnreadCountEnabled: true } },
});

// The user has seen the newest messages.
channel.markReadLocally();

With offline support, the reset is saved in the offline database too.

Read state in threads

A thread keeps its own read state, in the read field of thread.state, one entry per participant. Its fields are named differently from a channel's:

thread.ownUnreadCount is the current user's count.

const ownUserId = client.userId;

const unsubscribe = thread.state.subscribeWithSelector(
  ({ read }) => ({
    unread: ownUserId ? (read[ownUserId]?.unreadMessageCount ?? 0) : 0,
  }),
  ({ unread }) => {
    console.log(`${unread} unread replies`);
  },
);

What changes it:

• a new reply: the author's entry goes to 0 unread, and every other entry gets 1 more, except the current user's while the thread is active;
• message.read for the thread: that user's entry goes to 0 unread;
• notification.mark_unread for the thread: the current user's entry takes the event's values.

A thread counts every new reply from someone else as unread, except while the thread is active. The channel's other rules (silent, shadowed, muted author or channel, read events off) don't apply to threads.

Thread.markRead() marks the thread read. It sends nothing when the current user has nothing unread, unless you pass { force: true }. An active thread marks itself read whenever it has unread replies, at most once a second, through the thread's markReadRequest handler if one is registered. To mark a thread unread, call Channel.markUnread({ thread_id: thread.id }).

Thread replies don't count toward the channel's unread count, and reading a thread doesn't change the channel's read state. The number of threads with unread replies is unreadThreadCount in client.threads.state, explained in What channels and threads hold.

Used in

• Read state, unread and receipts
• Channel lists
• Replies and threads