Slack offers both paid and free versions of its software. The service is highly functional and is fully compatible with a range of third-party solutions, enabling its users to communicate with a large number of people simultaneously. The messenger launched in beta mode back in 2013 and now boasts more than 1 million users. Slack Technologies is a tech firm established by Flickr co-founder Stewart Butterfield whose products include a corporate messaging service that is tipped to be "the death of Skype" and a software-based collaboration hub.