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    "name": "CumulativeLayoutShift.com",
    "url": "https://www.cumulativelayoutshift.com"
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      "@type": "Metric",
      "name": "Cumulative Layout Shift",
      "alternateName": "CLS",
      "description": "Cumulative Layout Shift (CLS) is a Core Web Vitals metric that measures the visual stability of a webpage by quantifying unexpected layout movement during the page's lifetime. It is calculated as the maximum session-window score across all layout shift events, where each event score is the product of the impact fraction and the distance fraction.",
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          "targetDescription": "The degree to which visible page content remains stable in position during and after page load, without unexpected movement."
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          "text": "Cumulative Layout Shift (CLS) is one of three Core Web Vitals metrics used by Google to evaluate page experience. It measures visual stability — specifically, how much the visible content on a page unexpectedly shifts position during the loading process.",
          "sourceUrl": "https://www.cumulativelayoutshift.com/what-is-cumulative-layout-shift.html",
          "pageTitle": "What Is Cumulative Layout Shift?",
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          "text": "The CLS score is a composite score that accounts for both the proportion of the viewport affected by unexpected movement and the distance elements traveled relative to the viewport size. A score of 0 means no layout shifts occurred. Higher scores indicate greater visual instability.",
          "sourceUrl": "https://www.cumulativelayoutshift.com/cumulative-layout-shift-score.html",
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          "text": "A good CLS score is 0.1 or below. This is the threshold required to pass the Core Web Vitals assessment and earn a Good page experience designation in Google Search Console. Scores between 0.1 and 0.25 are rated Needs Improvement; scores above 0.25 are rated Poor.",
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      "name": "Core Web Vitals",
      "description": "Core Web Vitals are a set of three metrics defined by Google that measure distinct dimensions of real-world page experience: Largest Contentful Paint for loading performance, Interaction to Next Paint for responsiveness, and Cumulative Layout Shift for visual stability. Pages must pass all three thresholds at the 75th percentile of real-user field data to earn a Good page experience designation in Search Console.",
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          "text": "Core Web Vitals are a subset of web performance metrics that Google has designated as the most important indicators of real-world user experience on the web. They were introduced in May 2020 and began affecting Google search rankings in June 2021 through the Page Experience update.",
          "sourceUrl": "https://www.cumulativelayoutshift.com/cumulative-layout-shift-core-web-vitals.html",
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          "text": "Google's Core Web Vitals assessment evaluates each metric independently using field data from the Chrome User Experience Report. A page is rated based on the 75th percentile of real-user measurements collected over the preceding 28 days. All three metrics must pass to earn a Good page experience designation.",
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    {
      "entityId": "e_003",
      "@type": "Metric",
      "name": "Layout Shift Score",
      "description": "The Layout Shift Score is the per-event score for an individual layout shift, calculated as the product of the impact fraction and the distance fraction. Multiple Layout Shift Scores within a session window are summed to produce the window score; the maximum window score across the page's lifetime becomes the final CLS value.",
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          "text": "Each individual layout shift event produces a score calculated from two fractions: Layout Shift Score = Impact Fraction × Distance Fraction. Multiple elements can shift simultaneously in a single event; the impact fraction covers all shifting elements and the distance fraction uses the greatest distance moved by any single element.",
          "sourceUrl": "https://www.cumulativelayoutshift.com/cumulative-layout-shift-score.html",
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      "entityId": "e_004",
      "@type": "Concept",
      "name": "Impact Fraction",
      "description": "The impact fraction is the portion of the viewport area affected by a layout shift event, calculated as the union of a shifted element's previous and current positions divided by the total viewport area. It is one of two multiplicative components of the Layout Shift Score.",
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          "text": "The impact fraction is the fraction of the viewport (by area) affected by the shift. It is calculated as the union of the element's previous position and current position, divided by the total viewport area. If an element's combined before-and-after positions cover 60% of the viewport, the impact fraction is 0.60.",
          "sourceUrl": "https://www.cumulativelayoutshift.com/cumulative-layout-shift-score.html",
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      "@type": "Concept",
      "name": "Distance Fraction",
      "description": "The distance fraction is the largest distance any single unstable element moved during a layout shift event, divided by the greater of the viewport's width or height. It is one of two multiplicative components of the Layout Shift Score.",
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          "text": "The distance fraction is the largest distance any single unstable element moved during the shift, divided by the greater of the viewport's width or height. If an element moved 150px and the viewport is 900px tall, the distance fraction is 150 divided by 900, or 0.167.",
          "sourceUrl": "https://www.cumulativelayoutshift.com/cumulative-layout-shift-score.html",
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      "@type": "Concept",
      "name": "Session Window",
      "canonicalLabel": "Layout Shift Session Window",
      "description": "A session window is the grouping unit used in the CLS calculation since June 2021. Layout shifts are grouped into windows of up to five seconds with no gap of more than one second between consecutive shifts. The CLS score is the highest-scoring session window observed during the page's lifetime, preventing long-lived pages from being penalized disproportionately.",
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          "text": "Since 2021, Google uses a session window approach for CLS. Layout shifts are grouped into windows of up to five seconds where no more than one second passes between any two consecutive shifts. The CLS score reported is the maximum score of any single session window — the worst burst of instability during the page's lifetime.",
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      "name": "CumulativeLayoutShift.com CLS Checker",
      "alternateName": "CLS Checker",
      "description": "CumulativeLayoutShift.com is a free online tool that tests any URL for Cumulative Layout Shift using the Google PageSpeed Insights API. It returns a CLS score, a Good/Needs Improvement/Poor rating, field data from the Chrome User Experience Report, and a breakdown of specific shifting elements with automated cause-inference badges.",
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          "text": "CumulativeLayoutShift.com is a free tool that tests any URL for Cumulative Layout Shift. It returns the CLS score, a Good/Needs Improvement/Poor rating, field data from real Chrome users, and a breakdown of the specific elements causing layout shifts — with automated cause inference identifying why each element shifted.",
          "sourceUrl": "https://www.cumulativelayoutshift.com/",
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      "name": "Google PageSpeed Insights",
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      "description": "Google PageSpeed Insights is a free web performance analysis tool that evaluates URLs using the Lighthouse engine for lab data and the Chrome User Experience Report for field data. It returns scores and diagnostics for all Core Web Vitals, including Cumulative Layout Shift, with element-level shift attribution when available.",
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          "text": "Google PageSpeed Insights returns both lab data from a Lighthouse simulation and field data from the Chrome UX Report for the same URL side by side. The lab results include a breakdown of specific elements contributing to layout shifts, including their individual shift scores and — in many cases — the preceding and current positions of each element.",
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          "text": "The Chrome User Experience Report is the underlying dataset that powers both Search Console's Core Web Vitals report and the field data shown in PageSpeed Insights. It is available via a free REST API and a BigQuery dataset providing monthly snapshots of Core Web Vitals data for millions of origins worldwide.",
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      "@type": "Metric",
      "name": "Largest Contentful Paint",
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      "description": "Largest Contentful Paint (LCP) is a Core Web Vitals metric that measures loading performance by recording the time from page initiation to when the largest visible content element — typically a hero image or large text block — is fully rendered. The Good threshold is 2.5 seconds or below at the 75th percentile of real-user sessions.",
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          "text": "LCP measures the time from when a user initiates a page load to when the largest content element visible in the viewport is rendered. The LCP thresholds are: Good at 2.5 seconds or less, Needs Improvement between 2.5 and 4 seconds, and Poor above 4 seconds.",
          "sourceUrl": "https://www.cumulativelayoutshift.com/cumulative-layout-shift-core-web-vitals.html",
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          "text": "INP measures the latency of all user interactions with a page during its entire lifetime and reports the worst-case interaction latency. It replaced First Input Delay in March 2024. The INP thresholds are: Good at 200 milliseconds or less, Needs Improvement between 200 and 500 milliseconds, and Poor above 500 milliseconds.",
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      "description": "The Page Experience signal is Google's composite ranking signal incorporating Core Web Vitals (LCP, INP, CLS), HTTPS usage, and the absence of intrusive interstitials. Incorporated into Google's search ranking algorithm in June 2021, it functions as a tiebreaker signal — meaningful in competitive SERPs — rather than a primary ranking factor.",
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          "text": "Google officially incorporated Core Web Vitals into its ranking algorithm beginning in June 2021 through the Page Experience update. Google has consistently described Core Web Vitals as a tiebreaker rather than a dominant ranking factor — in highly competitive SERPs where multiple pages have comparable content quality, better Core Web Vitals performance can provide a ranking advantage.",
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          "pageTitle": "Cumulative Layout Shift and SEO — How CLS Affects Search Rankings",
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      "name": "Layout Instability API",
      "description": "The Layout Instability API is a browser API that detects and records layout shift events by tracking when visible DOM elements change position between animation frames without a preceding user-initiated input. It is the underlying mechanism by which browsers measure Cumulative Layout Shift, exposing impact fraction, distance fraction, and source element data for each shift event.",
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          "text": "CLS is calculated using the browser's Layout Instability API, which tracks every moment a visible element moves from one position to another without the user initiating the movement. Each such movement is called a layout shift. The API records the impact fraction, distance fraction, and source elements for each shift event.",
          "sourceUrl": "https://www.cumulativelayoutshift.com/what-is-cumulative-layout-shift.html",
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