No, it’s wasn’t just you. Slack indeed went down due to an outage of some sort that appeared to have begun some time around 7:30PM ET. User-reported issues spiked on DownDetector.com, and the app was largely inaccessible, with posts not getting marked as read or not going through at all. The issues affected both the mobile and desktop versions of the app. Slack says it's fully restored service, but it did not disclose the source of the disruption.
Slack confirmed the outage on its status website, intially writing, “Users have reported general performance issues such message sending failures and timeouts. We’re working to get things back to normal as quickly as possible and will provide an update shortly,” at 7:53PM ET. Shortly after at 8:02PM ET, the page was updated with, “Users are unable to connect to Slack. We are investigating and will provide an update shortly.”
The issues seemed widespread, although it’s not clear whether it was isolated to any one part of the US. DownDetector reports indicated the outage was hitting the West Coast rather hard, but that may be a factor of Slack’s higher usage among tech companies.
At 8:43PM ET, Slack updated its status page with, “Some customers may be seeing improvements, but we’re still investigating the connectivity issues. We’ll be back in 30 minutes with another update. Thank you for bearing with us.” Shortly after, Slack said customers may be experiencing performance improvement,s but it’s still working to fully restore service.
Finally, at 10:26PM ET, Slack said, “We have fully restored service and everyone should be able to connect to Slack now. If you have any further trouble, please let us know at firstname.lastname@example.org. We’re very sorry for the disruption. We appreciate your patience as we worked to get everyone back online.”
Update May 12th, 9:07PM ET: Added updates from Slack’s status website.
Update May 12th, 11:04PM ET: Added that Slack has restored service. The headline has been updated to reflect this fact.