Instagram has finally outlined details of how its feed sorting algorithm works and offered reasons for why it works the way it does. To begin with, the company has clarified that the algorithm is actually a big improvement to the one that was in place prior to mid-2016. Not only are more people than ever using the app more often, the algorithm has decreased the chances that a user will miss posts from their friends. As contentious as its algorithm has been at times, it now ensures that users see around 90-percent of their friends' posts. That's compared to around half of a user's friends' posts being missed and as many as 70-percent of all posts being missed. So the algorithm isn't without good reason and seems to have improved things overall.
As to the algorithm itself, there are six factors considered by the built-in machine learning which determine what shows up and where it shows up in a user's feed. Some of those are more obvious such as how recent a post was published and how close the person is to the user in question. Newer posts are prioritized over others, as are those published by friends and family of the user. However, it also takes into account whether or not the user has shown interest in a given topic through machine vision and analysis of past behavior. Of course, the problem with only using those factors is that it could easily result in Instagram only showing posts of a select few people. So Instagram's algorithm also pulls posts from a larger group of people, which reportedly increases as the number of users followed does. That means that as the number of people a user follows grows, Instagram's algorithm increases the number of those people whose posts it will include near the top of the feed.
Meanwhile, the system also takes into account how often and for how long a user is in the app on average. For users who only jump on for short sessions, only the best posts will make it to the top. The same goes for users who aren't interacting with the app as often. For those who use it more, the algorithm goes deeper to show more content from across a wider array from those people the user is following. None of that means that users can't continue to scroll through Instagram to see every post from every follower if they choose to do so, either, the company explained. It also doesn't block or hide user content from the feed, downrank users, or play favorites with video or photo content. There's also no chance, at this point, that the company is going to revert to previous chronological orders since that would only make everything more complicated.