lazyloaded

Lazyloaded is a term used in web development to describe resources that have been loaded using lazy loading techniques. In this context, a resource becomes lazyloaded when its loading is deferred until it is likely to be needed, rather than loading at initial page render. This concept is commonly applied to images, iframes, scripts, and data requests to improve perceived performance and reduce initial bandwidth.

How lazyloading works varies by approach. Native browser support includes the loading attribute, such as loading="lazy" on images and iframes, which instructs the browser to postpone fetching until near the viewport. Programmatic approaches use an IntersectionObserver to detect when an element approaches visibility and then trigger loading or rendering. Dynamic imports can be used to defer heavy JavaScript modules until user interaction or when a component enters view. Placeholders, skeleton screens, or fixed-size containers help prevent layout shifts while content is being lazyloaded.

Benefits of lazyloaded resources include faster initial render, lower data consumption on first load, and improved performance metrics like First Contentful Paint and Largest Contentful Paint, especially on slower networks. However, there are challenges to manage, such as potential layout shifts if dimensions aren’t reserved, SEO and accessibility considerations, caching behavior, and increased complexity in code and testing.

Best practices emphasize defining explicit dimensions or aspect ratios, using responsive images with srcset and sizes, prioritizing critical content, and testing with performance tools to balance perceived speed and completeness. Lazyloading is widely supported through native attributes and JavaScript APIs and is commonly integrated into modern web frameworks.