How Slack Rebuilt Notifications 📣

Slack rebuilt its notification system to reduce noise by replacing years of inconsistent, tightly coupled behavior with a unified model. The redesign separates what activity users see from how they receive interruptions, while aligning desktop and mobile settings. By combining backend migration strategies, auto-saving controls, and shared UI patterns, Slack aims to make notifications predictable and easier to manage.

Diagnosing Notification Overload

• Notification frustration is common, especially for users in many channels.
• Notification issues are among Slack’s top three sources of Customer Experience tickets.
• The underlying problem was architectural as well as behavioral:
  • Desktop and mobile used conflicting preference systems.
  • Equivalent settings, such as “Nothing” and “Off,” behaved differently across clients.
  • Activity preferences were coupled to push delivery.
  • Settings could fall out of sync between desktop and mobile.
  • Advanced options were scattered or difficult to discover.

A Unified Notification Model

Slack introduced a simpler set of controls:

• Channel notifications now offer:
  • All new posts
  • Mentions
  • Mute
• Push notifications have separate on/off controls across desktop and mobile.
• Advanced features, including mobile “badge all unreads,” are easier to find.
• Global preferences use consistent structure and language.
• Simplified preference logic improves synchronization between clients.

Refactoring Preferences Safely

• Slack migrated users from four conflicting preference systems to a unified model.
• The new model separates:
  • Desktop activity: Everything or Mentions
  • Desktop push: desktop_push_enabled set to true or false
  • Mobile activity and push behavior: Everything, Mentions, or Nothing
• Rather than changing millions of database records directly, Slack used read-time interpretation to preserve backward compatibility and allow rollback.
• Existing “Off” settings now behave as “Mentions” with push disabled.
• A backfill populated the new desktop push preference based on users’ previous settings.
• This preserves in-app awareness while allowing push interruptions to be controlled independently.

Auto-Saving and Clearer Controls

• The previous modal required users to press Save, which caused accidental abandoned changes.
• The redesigned interface applies changes immediately through auto-save.
• Users can independently choose what activity to see and how they want to receive it.
• Shared React components replaced legacy mobile-specific UI code, improving consistency across platforms.
• Users can now, for example, view all activity while receiving push notifications only for mentions.

Slack’s approach demonstrates that reducing notification noise requires more than a visual redesign. Separating activity from delivery, simplifying preference states, and keeping clients synchronized gives users clearer and more reliable control over interruptions.