For Meta traffic, the landing page has to do two jobs at once: keep the click emotionally hot by matching the ad's claim and creative, and send clean conversion signals back to Meta so delivery can optimize.
Meta recommends using Pixel standard events to understand actions people take on your website and to log conversions for optimization and audience building. The practical setup is Pixel on the page plus the correct standard event (often Lead or CompleteRegistration) fired on the thank-you or confirmation state, not on a button click.
If you are optimizing for web events, Meta's Aggregated Event Measurement is part of the ecosystem you may need to account for on the platform side. The foundation is still page-side: correct event, fired once, on the real conversion moment.
Message match and a single true conversion event. Do not fire conversion events on partial actions.