It also has instant messaging, file transfer, debit-based calls to landline and mobile telephones (over traditional telephone networks), and other features. Skype ( / s k aɪ p/) is a proprietary telecommunications application that specializes in providing VoIP-based videotelephony, videoconferencing and voice calls. Videoconferencing, VoIP and Instant messaging Windows, macOS, Linux, Android, iOS, iPadOS, HoloLens, Xbox One, Xbox Series X/S