Voice calling and online chat application owned by Microsoft. It was founded by Priit Kasesalu and Jaan Tallinn and was originally released on August 29, 2003.
Group messaging app built as a cloud-based team collaboration tool, Slack launched August 2013 and was co-founded by Stewart Butterfield, Eric Costello, Cal Henderson, and Serguei Mouracho.
Cloud communications company which allows sending and receiving calls and text messages over HTTP. The company was founded in 2007 by Jeff Lawson, Evan Cooke and John Wolthuis.
Popular cross-platform instant messaging application released in January of 2010 and acquired by social networking company Facebook on February 19, 2014.