Adam Mosseri has published a full explainer article of Instagram on the company blog, including ranking for its various formats.
Each part of the app - Feed, Stories, Explore, Reels and Search - uses its own algorithm.
Instagram uses signals to rank Feed posts based on factors like posts you’ve liked and and engaged with. The most important signal is your activity (likes, shares, comments and saves), followed by information about the post (location, popularity); information about the post’s author; and your history of interacting with the person who posted.
For Stories, viewing history is the most important signal, followed by engagement history and relationships (like friends or family).
The most important actions in the Explore feed include likes, saves, and shares. Instagram prioritises information about the post first, followed by your previous Explore activity; your history of interacting with the person you posted; and information about the post.
And for Reels, your activity comes first, followed by your history of interacting with the person who posted; information about the Reel; and information about the Reels’ author.
What brands should take from this:
Accounts that have been Favourited show up higher in Feed. Use call-to-actions in your posts or in Reels to get followers to Favourite your account.
Make content shareable - think entertainment value over product sales - and turn Reels into useful resources by creating how-to guides or tips for product care. The more people share and save your posts, the more likely you are to reach others.
Invest in feed posts and Reels over Stories for growth. Stories are more likely to only be seen by the select few that engage with you the most.
See if your account is eligible to appear in Search or as a suggested account by going to Account Status in your Settings.