What metric should be tracked to understand how many unique users see your post?

The correct metric to track for understanding how many unique users see your post is reach. Reach specifically measures the total number of unique individuals who have seen your content. By focusing on reach, marketers can gain insights into the extent of their audience exposure, helping to identify the effectiveness of their posts in attracting attention.

In contrast, audience growth rate measures the speed at which a brand's audience is increasing over time, which does not provide information about individual post visibility. Engagement rate reflects interactions (likes, shares, comments) relative to the number of followers but doesn't indicate how many unique users viewed the post. Impressions count the total number of times a post has been seen, including multiple views by the same user, which can misrepresent the actual number of unique viewers. Therefore, reach is the most relevant metric for assessing the unique viewership of social media posts.