Slack's Two-Day Outage Leaves Messaging and Bots Offline

Slack experienced a significant outage spanning February 26 and 27 that impacted multiple core functions. While the platform restored most capabilities by Thursday, residual problems persisted with messaging functionality, custom applications, and bot integrations. Slack Connect users faced an additional complication: the @ mention notification system failed to alert colleagues when they were tagged. Downdetector logged approximately 3,000 incident reports during the peak disruption.

By Thursday morning, Slack announced that the majority of its services had returned to normal operation. Customers still encountering difficulties were instructed to refresh their Slack instance using Command + Shift + R on Mac or Ctrl + Shift + R on Windows and Linux systems.

Slack team's response to the outage, including Slack Connect tips

The platform's malfunction stemmed from two distinct technical problems. Slack attributed the primary issue to "related to Events API and is a symptom of an earlier incident about trouble connecting to or loading Slack," while a separate, unrelated glitch in Slack Connect prevented notification delivery. The company's internal systems team flagged the disruption at approximately 1:00 p.m. EST on February 26, with some staff unable to compose messages.

During Wednesday evening, Slack's status dashboard reported: "We're continuing to diligently work on database shard repair and have made progress on restoring affected replicas, though users may still be experiencing impact." Engineers subsequently focused on "re-processing of the backend job to attempt to serve queued Events API requests." For those struggling with Slack Connect mentions, the company provided these remediation steps:

1. Open the Slack desktop app, then click Help in your computer's top menu bar. (On Windows 10, click the three horizontal lines icon in the top left of the Slack app.)
2. Select Troubleshooting.
3. Click Clear Cache and restart.

Slack characterized the root cause as "a symptom of an earlier incident" without elaborating further. Messages, workflows, threads, and other API-dependent features were among the last components to resume normal operation.

Past outages and Slack's place in the market

This disruption marked Slack's most severe outage since July 2023. The platform had experienced multiple service interruptions during 2022 and again in January 2021.

Slack functions as a key component within Salesforce's Agentforce generative AI initiative. The platform faces competition from Microsoft Teams, Google Chat, and Pumble.