Excellent question, it highlights a critical web performance trade-off.
Quick Answer: Yes, when organised properly, lazy loading drastically improves initial page load performance by deferring the download of offscreen content like images and videos.
The goal is to make the site feel faster to the user by loading only what they need to see first.
Your concern about lag is valid, as poor implementation can certainly create a jarring user experience. The primary benefit of lazy loading is a faster initial render of the page because the browser isn’t trying to download every single image and video embed at once.
First, this positively impacts core performance metrics by prioritising the content visible in the viewport.
Second, to avoid that ‘janky’ scrolling you mentioned, it is crucial that placeholders are used for the deferred images, specifying their dimensions so the browser reserves the correct space, which prevents the page layout from shifting as the user scrolls.
Finally, you must avoid the common mistake of lazy loading assets that are “above the fold”—such as your logo or main hero image—as this would actively harm performance by delaying the very content the user needs to see immediately.
Cheers,
Jeff
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