Community ArticleCommunity articles are authored by SitePoint Premium contributors. Content is screened before publication, and SitePoint reserves the right to moderate or remove articles that violate our guidelines. Views expressed are those of the authors and do not necessarily reflect those of SitePoint.Every interesting product decision starts with the same question: what are people actually doing on my site? Which buttons get clicked, how far visitors scroll, where they hesitate, and where they quietly leave. You can answer all of this with a few well-placed lines of JavaScript and no heavyweight SDK required. In this guide, we'll build a small, dependency-free behavior-tracking layer from scratch. You'll learn how to capture clicks, scroll depth, time on page, and custom events; how to send that data to your server reliably (this is the part most tutorials get wrong); and how to do it all without hurting performance or trampling user privacy.…