Instagram is a photo and video-sharing social networking service owned by Facebook, Inc. It was created by Kevin Systrom and Mike Krieger, and launched in October 2010 exclusively on iOS. A version for Android devices was released a year later, in April 2012, followed by a feature-limited website interface in November 2012, and apps for Windows 10 Mobile and Windows 10 in April 2016 and October 2016 respectively. The app allows users to upload photos and videos to the service, which can be edited with various filters, and organized with tags and location information. An account's posts can be shared publicly or with pre-approved followers. Users can browse other users' content by tags and locations, and view trending content. Users can "like" photos, and follow other users to add their content to a feed. The service was originally distinguished by only allowing content to be framed in a square (1:1) aspect ratio, but these restrictions were eased in 2015. The service also added messaging features, the ability to include multiple images or videos in a single post, as well as "Stories"—similar to its main competitor Snapchat—which allows users to post photos and videos to a sequential feed, with each post accessible by others for 24 hours each. After its launch in 2010, Instagram rapidly gained popularity, with one million registered users in two months, 10 million in a year, and ultimately 800 million as of September 2017. In April 2012, Facebook acquired the service for approximately US$1 billion in cash and stock. As of October 2015, over 40 billion photos have been uploaded to the service. Although praised for its influence, Instagram has been the subject of criticism, most notably for policy and interface changes, allegations of censorship, and illegal or improper content uploaded by users.