Instagram Insights
Why it matters for creators
Insights is the free baseline, and for most of what a creator needs to decide it is enough. It answers what performed, when your audience is on, and roughly who they are.
Two limits are worth knowing before you rely on it. Retention is finite — Instagram keeps most metrics for a rolling window, so a year-on-year comparison is something you have to have recorded yourself, not something you can go back and look up. And several Insights numbers are not available through Meta's API at all without the insights permission, which is why some tools show you data the app shows and others do not.
For anything about conversion rather than attention, Insights stops early: it can tell you a post reached 40,000 people, not how many of them ended up in a conversation. Engagement rate is the ratio it does not calculate for you, and it is usually the more honest number.