Terrible messenger. Viber doesn't keep its own list of contacts, unlike Telegram or Slack, or Skype. To manage contacts it demands access to my phone's contacts. Viber doesn't keep chat history in the cloud. I had to uninstall at one point, then installed back and lost years of messages. To keep history, it demands access to read and write into Google Drive. I won't give it access to my files, because it is a Chinese app with Russian investors, so I don't trust them to follow privacy laws.