Why does my web page jump around while it loads?
If an image has no width and height set in the page, the browser does not know how much space to leave for it. The text appears, then the image arrives and shoves everything down. On a phone that means the button you were about to tap moves and you tap something else. Google calls this cumulative layout shift and measures it as one of its three Core Web Vitals.
Why it matters
Beyond the ranking effect, it is the thing visitors most often describe as a page feeling "broken". Text they were reading moves. A link they were about to click is replaced by an advert. Forms shift while they are typing. It makes a site feel cheap in a way that is hard to name but easy to feel.
What causes it
- Images and videos without width and height attributes.
- Adverts, embeds and cookie banners inserted above content after it has loaded.
- Web fonts arriving late and reflowing text at a different size.
- Content injected by scripts, such as a notification bar, at the top of the page.
How to check
Our check counts images on your home page that have no width and height. Google's PageSpeed Insights reports the layout shift score and highlights the elements that moved.
How to fix it
Give every image and video a width and height attribute, which lets the browser reserve the space before the file arrives. Modern platforms, including WordPress, add these automatically to images inserted through the editor, but not always to images in themes, sliders or page builders. Reserve space for adverts and embeds with a fixed-height container. Load web fonts with the "swap" display setting and match the fallback font's size as closely as you can. Put cookie banners and notification bars in a fixed position at the bottom or overlaid, never inserted above the content.
Not sure how your own site does on this? Run the free check: it takes about twenty seconds and reports on this and thirty other things.