And a critical component of the company's success can be illustrated by a recent tweet from it's CEO and co-founder, Stewart Butterfield.
"I'm glad he's having a great life, but Stewart should enjoy his gains now as this is short term thing. Their customer services is so awful, so this won't last when the people who helped build slack abandon the platform," Patel posted.
Butterfield is a busy guy — he leads a company with more than 1600 employees in 10 offices around the world. But he took the time to respond to the tweet, seeking feedback.
"No one is more critical of Slack than me (ask anyone who works at the company!), but the one thing I'd say we do particularly well is service & support," Butterfield tweeted. "So I'd love to hear more about your experience. Feel free to reply or [direct message]."
The next day Patel tweeted, "The customer support folks were on it today and they have been helpful," adding Slack does "take customer service seriously for sure."
And Slack's rapid growth is, at least in part, due to just that — the company's dedication to listening to its customers.
"We will take user feedback any way we can get it. In the app, we include a command that people can use to send us feedback. We have a help button that people can use to submit support tickets," Butterfield told First Round in 2015.
Customer feedback has been a cornerstone of the company practically since its inception.
The platform that is now Slack was a messaging system originally salvaged from office software Butterfield and his team had built at a failed gaming company he founded. Work began on Slack in 2012, and by March 2013, Butterfield and his team were aggressively trying to get other companies to use the product for feedback.
"Sometimes you will get feedback that is contrary to your vision," Butterfield said, but even so, "we looked at our customers, really just testers at that point, and we paid extra attention to the teams we knew should be using Slack successfully."
After Slack launched in 2014, Butterfield also watched Twitter closely for user feedback.
"We're pretty fastidious about tagging all of these incoming messages, collating and entering and retaining the data that people are sending us," Butterfield said.
In January 2015, Slack had fewer than 1 million daily active users. But as of January, it had more than 10 million daily active users and 85,000 paying customers, the company announced.
And Butterfield is still reading customer comments on Twitter — and responding to them personally.
Earlier this month, on June 5, Butterfield even responded to a Twitter user looking for a fast way to take a screenshot in Slack.
Disclosure: Comcast Ventures, the venture arm of Comcast, is an investor in Slack. Comcast owns CNBC parent company NBCUniversal.
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