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Performance

Largest Contentful Paint

Largest Contentful Paint measures when the largest visible content element in the viewport has rendered.

Largest Contentful Paint measures when the largest visible content element in the viewport has rendered. Optimization becomes meaningful when real-user data, repeatable lab tests, and an explicit performance budget are used together. The concept is closely related to Core Web Vitals and Image Optimization.

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Core Web Vitals

Image Optimization

Time to First Byte

Critical CSS

FAQ

Largest Contentful Paint

Why do lab and field values differ for LCP?
Lab tests run under fixed conditions, whereas field data reflects real devices, networks, and locations. A good lab score therefore does not protect against poor field results. Core Web Vitals assessment relies on field data, and the lab serves for root-cause analysis and for verifying changes.
Should the hero image be lazy loaded?
No, the image in the initial viewport should load right away with high priority. Delaying the LCP element directly worsens the metric. Lazy loading belongs on elements below the first screen. A quick test run reveals whether the hero image is being delayed by accident.
What most often slows down Largest Contentful Paint?
Frequent causes are a slow server response, oversized or late-discovered images, render-blocking CSS and JavaScript, and web fonts that delay text. Compressing images alone often misses a sluggish server. The analysis should therefore cover the whole chain from request to rendering.
Which element is measured as the Largest Contentful Paint?
The measured element is the largest visible one in the viewport, usually a hero image, a video poster, or a large text block. It can differ by device and screen width. It should therefore be identified separately for mobile and desktop and optimized deliberately.
What LCP value counts as good?
An LCP of 2.5 seconds or less counts as good. It is assessed at the 75th percentile of field data, meaning real visits, rather than from a single lab test. A value above the threshold means a quarter of visits or more see the largest element later.