Cumulative Layout Shift is a Core Web Vitals metric that measures visual instability from unexpected layout shifts during a page visit, including shifts after initial load.
It matters because technical issues can prevent great content from being discovered, rendered, indexed, or trusted. Strong technical foundations protect rankings during redesigns, migrations, content expansion, and platform changes.
Example
A late-loading image without reserved space can push an article paragraph downward while someone is reading. Reserve appropriate dimensions and check the page beyond initial load, because unexpected layout movement can occur later in the visit too.