LCP Breakdown Checker
LCP Breakdown Checker
Why is your LCP slow? This splits the real-user Largest Contentful Paint into its 4 sub-parts (server, load delay, download, render) and names the biggest lever to fix. From Chrome CrUX.
LCP sub-parts are reported mainly for image LCPs on higher-traffic sites. Smaller sites may show « no data ».
How the LCP Breakdown Checker works
Largest Contentful Paint (LCP) is the Core Web Vital that measures how fast the main content of a page appears. A bad LCP number tells you there is a problem, but not where. This tool splits the real-user LCP (from Chrome CrUX) into its four sub-parts so you know exactly what to fix.
The four sub-parts
- TTFB: time to the first byte from the server. High = slow backend or no caching.
- Load delay: gap before the LCP image even starts downloading. High = the image is discovered too late or blocked by other resources.
- Load time: how long the image takes to download. High = the image is too heavy or served without a CDN.
- Render delay: the image is ready but the browser paints it late. High = render-blocking JS/CSS or long tasks.
What you can do with it
Instead of guessing, you get the dominant phase and a concrete fix (speed up the server, preload the image, compress it, or unblock rendering). It also shows whether the LCP element is usually an image or text.
Frequently asked questions
What is a good LCP?
Google considers LCP good at 2.5 seconds or less (at the 75th percentile of real users), needs-improvement up to 4 seconds, and poor beyond that.
Why split LCP into sub-parts?
Two sites can both have a 4-second LCP for completely different reasons: one is slow on the server (TTFB), the other loads a huge image. The fix is different, so knowing the dominant phase saves hours.
Is this lab or real-user data?
Real-user data (field), from Chrome CrUX over the trailing 28 days. It reflects what actual visitors experienced, not a single simulated run.
My site has no breakdown, why?
LCP sub-parts are reported mainly for image LCPs and require enough traffic. A small site, or one whose LCP is usually text, may show limited data.
Data: real Chrome users via the public Chrome UX Report (CrUX), trailing 28 days. Free and open, no API key.