WhatsApp Messenger is a freeware and cross-platform instant messaging service for smartphones. It uses the Internet to make voice calls, one to one video calls; send text messages, images, GIF, videos, documents, user location, audio files, phone contacts and voice notes to other users using standard cellular mobile numbers. All data are end-to-end encrypted. It also incorporates a feature called Status, which allows users to upload photos and videos to a 24-hours-lifetime feed that, by default, are visible to all contacts. By February 2016, WhatsApp had a user base of over one billion, making it the most popular messaging application at the time.