Cumulative Layout Shift (CLS)

How CLS is scored

• A layout shift happens when a visible element changes position from one frame to the next.
• Shifts within 500 milliseconds of a tap, click or key press are treated as expected and left out.
• Shifts are grouped into session windows: bursts with less than a second between shifts, lasting at most five seconds.
• A page's CLS is the score of its worst window, judged at the 75th percentile of page loads, separately for mobile and desktop.

How embeds cause shifts

web.dev names third-party ads and widgets that resize themselves among the usual causes, along with images and videos of unknown size, web fonts that render at a different size from their fallback, and content inserted above what's already on screen. An embed that starts as a short box and then grows pushes everything below it down; if that happens in view, it counts.

Keeping embeds from shifting the page

• Reserve space: give the embed's container a min-height close to its final height.
• Place feeds and other tall embeds below the first screen where you can; shifts out of view don't add to the score.
• Set width and height on images so the browser knows their shape before they load.
• Don't insert banners or embeds above content the visitor is already reading.
• Check field data in PageSpeed Insights or Search Console after launch, not just a single lab test.

LinkedInEmbed's script snippet creates each frame at a modest starting height and then resizes it to fit. For a widget that's visible when the page opens, a min-height on its wrapper reduces the jump.