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Facebook Messenger -LRB- sometimes abbreviated as Messenger -RRB- is an instant messaging service and software application .. Facebook. Facebook. instant messaging. instant messaging. It is integrated with Facebook 's web-based chat feature and built on the open MQTT protocol .. Facebook. Facebook. chat. Facebook features#Messages and inbox. MQTT. MQTT. Facebook Messenger lets Facebook users send messages to each other .. Facebook. Facebook. It was launched as a standalone app on the Android and iOS operating systems in August 2011 and the functionality was then removed from the main Facebook app in April 2014 .. Facebook. Facebook. Android. Android ( operating system ). iOS. iOS. Facebook has also launched Facebook Messenger Lite , a basic app with a limited feature set for areas with low-speed Internet or old mobile devices .. Facebook. Facebook. A website interface is also available .. website interface. web application. Complementing regular conversations , Messenger lets users make video calls both in one-to-one interactions and in group conversations .. video calls. Videotelephony. Its Android app has integrated support for SMS and `` Chat Heads '' , which are round profile photo icons appearing on-screen regardless of what app is open , while both apps support multiple accounts , conversations with optional end-to-end encryption , and playing `` Instant Games '' , which are select games built into Messenger .. Android. Android ( operating system ). SMS. SMS. end-to-end encryption. end-to-end encryption. Some features , including sending money and requesting transportation , are limited to the United States .. In 2017 , Facebook has added `` Messenger Day '' , a feature that lets users share photos and videos in a story-format with all their friends with the content disappearing after 24 hours ; Reactions , which lets users tap and hold a message to add a reaction through an emoji ; and Mentions , which lets users in group conversations type @ to give a particular user a notification .. Facebook. Facebook. emoji. emoji. In March 2015 , Facebook announced that it would start letting businesses and users interact through Messenger with features such as tracking purchases and receiving notifications , and interacting with customer service representatives .. Facebook. Facebook. It also announced that third-party developers could integrate their apps into Messenger , letting users enter an app while inside Messenger and optionally share details from the app into a chat .. chat. Facebook features#Messages and inbox. In April 2016 , it introduced an API for developers to build chatbots into Messenger , for uses such as news publishers building bots to give users news through the service , and in April 2017 , it enabled the M virtual assistant for users in the U.S. , which scans chats for keywords and suggests relevant actions , such as its payments system for users mentioning money .. API. API. chatbots. Software agent. Additionally , Facebook expanded the use of bots , incorporating group chatbots into Messenger as `` Chat Extensions '' , adding a `` Discovery '' tab for finding bots , and enabling special , branded QR codes that , when scanned , take the user to a specific bot .. Facebook. Facebook. chatbots. Software agent. After being separated from the main Facebook app , Messenger had 600 million users in April 2015 , growing to 900 million in June 2016 , 1 billion in July 2016 , and 1.2 billion in April 2017 .. Facebook. Facebook