Browsing all of your unread messages from the desktop app lets you catch up on the messages you missed when you were away from Slack. While you're at it, you can act on those messages too:
Jump from the All unreads view to a channel or direct message (DM) to send a new message.
Note: For now, the All unreads view is only available from Slack on your desktop.
Set your All unreads view
From your desktop, click your workspace name in the top left.
Select Preferences from the menu.
Click Sidebar.
Check or uncheck the box next to Show All unreads.
Note: Messages in muted or archived channels aren't included in the All unreads view.
Navigate unread messages
From All unreads, manage how you'd like to view unread messages to help you prioritize work in Slack.
Sort unread channels
Decide how to prioritize your unread messages by changing how they’re sorted. You can sort messages alphabetically, by newest activity, or by oldest activity. On paid plans, you can also sort scientifically — a view tailored to how you use Slack.
Mark messages as read
Click Mark as Read to clear a channel's messages when you've finished reading them. You can also scroll to the bottom of the All unreads view and click Mark All Messages Read.
If you clicked Mark as Read too quickly, just click Undo to keep those messages in your All unreads view.
Save a channel's messages for later by clicking the arrow icon beside the channel name to collapse it. Click the arrow again when you're ready to read the unread messages.
Refresh for new messages
When new messages become available while in the All unreads view, the syncing arrows icon will appear in the header. Click the icon to reveal a fresh batch of unread messages.
