Understand Core Web Vitals correctly and jump straight to Google PageSpeed Insights for real data
This is not a self-running speed analyzer. Measuring real Core Web Vitals (LCP, INP, CLS) accurately requires actual Lighthouse/CrUX infrastructure that this page does not run itself. Below you get (1) a reference for the real Core Web Vitals metrics, and (2) a button that opens Google's official PageSpeed Insights tool with your URL pre-filled, so you get real data.
This button opens a new tab to pagespeed.web.dev with your URL pre-filled — the data returned is real data from Google (Lighthouse lab data plus CrUX field data when available), not a simulation.
LCP
Largest Contentful Paint
Measures loading performance — how fast the main content renders.
INP
Interaction to Next Paint
Measures responsiveness to user interactions. Replaced FID in March 2024.
CLS
Cumulative Layout Shift
Measures visual stability while the page loads.
FCP
First Contentful Paint
Time to first rendered content. A useful lab metric, but not part of the official Core Web Vitals.
TTFB
Time to First Byte
Server response time. Not a Core Web Vital itself, but influences LCP indirectly.
SI
Speed Index
How quickly content is visually displayed during load. A Lighthouse lab metric, not a Core Web Vital.
This is a Core Web Vitals reference and explainer tool, NOT a self-running speed analyzer. It helps you understand the 3 official Core Web Vitals — LCP (Largest Contentful Paint), CLS (Cumulative Layout Shift), and INP (Interaction to Next Paint) — with Good/Needs Improvement/Poor thresholds, and gives you a one-click link to run your URL through Google PageSpeed Insights (pagespeed.web.dev) for 100% real, accurate data straight from Google.
Accurately measuring Core Web Vitals requires either running a real Lighthouse audit (simulated browser, network throttling, CPU throttling) or querying the Chrome UX Report (CrUX) — Google's real user data. Google's public PageSpeed Insights API requires its own API key and has an extremely limited quota when used unauthenticated. Rather than show estimated or simulated numbers that could be mistaken for real measurements, this tool takes the transparent path: explain the concepts correctly and send you straight to the most accurate data source — Google's own PageSpeed Insights.
As of March 2024, Google's official Core Web Vitals consist of only 3 metrics: LCP (Largest Contentful Paint — loading speed, Good threshold ≤2.5s), CLS (Cumulative Layout Shift — visual stability, Good threshold ≤0.1), and INP (Interaction to Next Paint — responsiveness, Good threshold ≤200ms). FID (First Input Delay) has been officially retired by Google and replaced by INP, because INP measures the full lifecycle of an interaction rather than just the initial delay. FCP, TTFB, and Speed Index are useful lab metrics but are NOT part of the official Core Web Vitals set — many tools (including an earlier version of this page) incorrectly lumped them in.
Google's public PageSpeed Insights API without an API key currently has an effectively zero daily quota (verified), so it cannot reliably serve real traffic. Rather than build a dedicated Lighthouse-running backend (a significant server resource commitment) or show simulated numbers that could mislead, the most transparent and trustworthy option is to send you directly to Google's own official tool.
Page Speed & Core Web Vitals is useful when you need to complete a focused task quickly without installing desktop software, creating another account, or switching into a heavy workflow. It works well for quick checks, conversions, previews, cleanups, generation tasks, and everyday operations where speed and consistency matter. This is a Core Web Vitals reference and explainer tool, NOT a self-running speed analyzer. It helps you understand the 3 official Core Web Vitals — LCP (Largest Contentful Paint), CLS (Cumulative Layout Shift), and INP (Interaction to Next Paint) — with Good/Needs Improvement/Poor thresholds, and gives you a one-click link to run your URL through Google PageSpeed Insights (pagespeed.web.dev) for 100% real, accurate data straight from Google.
Start with a small sample so you understand how Page Speed & Core Web Vitals handles your input, then apply it to the full task. Review the important fields, copy or export the result, and test it in the place where you plan to use it. This keeps the tool fast while still giving you a practical quality-control step before production use.
Before using the output, check formatting, special characters, line breaks, file names, URLs, units, numbers, and mobile display when relevant. If the result affects SEO, code, design, business documents, analytics, or customer-facing material, compare it against your original requirement and fix any context-specific detail before publishing.
Because computing an accurate score requires running a real Lighthouse audit with Google's standardized network/CPU throttling profile. Showing a self-calculated number here would not reflect the data Google actually uses for ranking, so this page sends you straight to PageSpeed Insights, where the official, accurate score lives.
No. Google officially retired FID from the Core Web Vitals set in March 2024 and replaced it with INP. If you see a tool (including an older version of this page) still listing FID as a current Core Web Vital, that information is outdated.
Yes, they remain useful diagnostic lab metrics, but they are not part of the 3-metric set Google uses as an official ranking signal (Core Web Vitals). It's worth distinguishing them clearly when reading a performance report so you don't overweight them.
Yes, pagespeed.web.dev is completely free to use through its web interface (not the API). That's exactly why this page sends you there directly instead of calling the public API, which has a very limited quota.
Yes. Page Speed & Core Web Vitals is designed as a free browser-based utility for quick personal, learning, and professional workflows.
No. You can use Page Speed & Core Web Vitals directly in a modern browser such as Chrome, Edge, Safari, or Firefox.
Yes. The page is responsive and can be used on phones and tablets, although desktop is usually more comfortable for long input or repeated copy operations.
Use clean input, test with a small sample first, review the output carefully, and adjust any details that depend on your final use case.
In most cases, yes. You can use the generated or processed output in personal and commercial projects, but legal, financial, medical, or security-sensitive work should still be reviewed by a qualified person.
The tool is built for quick browser workflows. You should still avoid entering highly sensitive data unless the specific tool clearly states how the data is handled.
Many tools include copy or download actions. If a dedicated export is not available, you can usually copy the visible result manually.
Use professional software when you need multi-user collaboration, audit logs, access control, long-term storage, system integrations, or large-scale processing.
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