Slack rebuilt its notification system from scratch, replacing four legacy preference paradigms with a simplified three-option model (all messages, mentions, or mute). A key architectural change decouples notification intent from delivery, enabling consistent behavior across desktop and mobile. To avoid disruptive data migrations, Slack introduced a read-time transformation layer that maps legacy preferences to the new model. The redesign resulted in a 5x increase in user engagement with notification settings and a reduction in support tickets, with most users adopting the default mentions-and-DMs configuration.
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