What is Lazy Loading?

Lazy loading means delaying content that is not needed immediately when a page first opens. It is commonly used for below-the-fold images, videos, map widgets, comment areas, and heavy JavaScript modules.

The goal is to reduce the number and size of files the browser must download during the first render. Users see the page sooner, mobile bandwidth use goes down, and the server avoids unnecessary requests.

How It Is Implemented

Native image lazy loading: Images use the loading="lazy" attribute.
Intersection Observer: JavaScript starts loading when an element approaches the viewport.
Dynamic import: Heavy components are downloaded as separate bundles when needed.
Route-level code splitting: An application loads only the code for the current route.

What to Watch For

Lazy loading can hurt performance when applied to the wrong asset. A hero image or critical heading in the first viewport should usually load eagerly, because delaying it can worsen LCP. Images also need reserved width and height; otherwise layout shifts can affect CLS in Core Web Vitals.

For SEO, important text should not depend only on late-running JavaScript. Image alt text, proper sizing, and modern formats should be handled together with image optimization. The impact should be measured through Core Web Vitals, not assumed.

At Barlas Dijital, lazy loading decisions are usually validated with real user data as part of site speed optimization.