Definition: A social media algorithm is the set of ranking systems a network uses to decide which posts each person sees, and in what order, based on predictions of what that person is likely to engage with.
Also called: feed algorithm, ranking algorithm, the algorithm
Updated October 11, 2026
For every person, the network gathers candidate posts, scores each one with models that predict actions (a like, a comment, a share, watching to the end), and shows the highest-scoring posts first. The inputs are called signals. Per Instagram’s own “Instagram ranking explained” post, there are thousands of them, from when a post was shared to how a person has interacted with the account before.
Instagram says it does not have a single algorithm: Feed, Stories, Explore, Reels and Search each rank content differently. Per the same post, Feed weighs how likely you are to spend a few seconds on a post, comment, like, share or tap the profile, while Reels weighs how likely you are to reshare, watch to the end, like or visit the audio page. Other networks work the same way, so “the algorithm” usually means one surface on one platform.
Two posts go out the same morning. One is a link with a generic caption; the other is a carousel answering a common customer question. The carousel earns saves and comments in its first hour, so the feed shows it to more of the account’s followers and, on some surfaces, to people who do not follow it yet.
Organic reach is the number of unique people who saw a post or account through unpaid distribution (feeds, search, shares and recommendations), excluding anyone reached through ads.
Engagement rate is the percentage of people who interacted with a post (liked, commented, shared, saved or clicked) out of the people who saw it or follow the account.
A hook is the opening of a post (the first line of text, the first slide or the first seconds of a video) designed to make people stop scrolling and keep reading or watching.
The best time to post is the day and hour when your own followers are most likely to be online and engage, which differs by platform, audience and time zone.
Reach is the number of unique people who saw a post or account at least once in a given period.
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