Responsible JavaScript

We can measure layout stability with a metric called Cumulative Layout Shift (CLS). Unlike time-based metrics, CLS uses a decimal scoring system that quantifies how far elements have shifted in the viewport from their previous position (http://bkaprt.com/rjs39/03-05). A good CLS score is 0.1 or less, but this could always change as some user-experience metrics may evolve over time. In practice, the closer you can get this metric to 0, the better off you’ll be.