Definition
What is Data Layer?
A data layer is a JavaScript object (typically named dataLayer) that stores structured information about page content, user interactions, and e-commerce transactions. Google Tag Manager reads from the data layer to fire tags and pass variables to analytics and advertising platforms. Data is pushed into the layer using dataLayer.push() calls.
Why it matters
A well-structured data layer decouples your tracking logic from your site code, making analytics implementations more reliable, testable, and maintainable across engineering deployments.