Chrome UX Report: User Speed Data by Google from A to Z

The Chrome UX Report (CrUX) is a public data file offered by Google, which collects and anonymously analyzes real user experience data for web browsing using the Chrome browser.

Google's Chrome UX Report.

CrUX focuses on key metrics such as loading speed, interactivity, and content stability, providing valuable insights into how websites perform under real-world conditions.

In addition to the basic Core Web Vitals (LCP, INP, CLS), CrUX now provides extended data, newly added to our Domain Reports in monitoring. These insights offer a deeper understanding of how your site behaves in real conditions, including user segmentation by device, page load methods, and details on what hinders images at LCP.

CrUX vs. RUM and Synthetic Testing#

CrUX isn't the only way to measure speed for real users. We detail the differences between measurement types, their strengths and weaknesses, and recommended combinations in the article synth vs. CrUX vs. RUM.

However, Chrome UX Report is an authority for SEO and PPC. Google collects the data itself and uses it as a signal in search ranking and Google Ads Quality Score.

How is Data Measured in the Chrome UX Report?#

CrUX collects data directly from the Chrome browser from users who haven't opted out of web usage data sharing. Domains and URLs must have sufficient traffic for CrUX data to appear. The data is aggregated at the page and domain level, including additional information about connection speed, region, etc.

This makes CrUX data the only officially reported source of web speed that impacts your ranking and ad costs. However, even CrUX has its limitations that you must account for in practice:

• 28-day Rolling Average
  Technical changes take several weeks to reflect in CrUX values. CrUX doesn't say "INP is better from today"; it shows a gradual slope.
• Device Segmentation
  Data is collected separately for mobile, tablet, and desktop. The average user profile differs significantly between them.
• Visibility Threshold
  Both the domain and specific URLs must have sufficient traffic (estimated 10–15 thousand views per month), otherwise, data won't appear in CrUX.
• SPA vs. MPA
  For Single Page Applications, CLS and INP are measured cumulatively for the whole session, not just the first load. CrUX values tend to be worse for SPAs than classic MPAs, even if the "speed" feels similar. Details and Chrome's measurement method are further explored on the web.dev page about SPA and Web Vitals.

For debugging specific issues, CrUX data is insufficient. Use synthetic testing or, in advanced cases, RUM measurements for all users.

Conversely, at PageSpeed.ONE, we use the Chrome UX Report as authoritative metrics for business decisions (SEO impact, prioritization) and as a reference framework against which to compare synth and RUM results.

Why is Data from the Chrome UX Report Important and Where is It Used?#

CrUX is vital for developers, SEO experts, and digital marketers because it offers insights into real user data. From our experience, speed most commonly impacts:

• SEO
  Google includes Core Web Vitals user experience metrics in evaluating website search rankings. Better performance can lead to better search rankings.
• PPC Campaign Evaluation
  Website speed affects bounce rate and overall PPC campaign effectiveness. The speed can also influence the ad cost in Google Ads.
• Speed Measurement (UX)
  CrUX provides real data on page load speeds, allowing developers to enhance user experience. By analyzing this data and optimizing, you can achieve faster site performance, leading to higher user satisfaction. It also allows you to easily compare your site with competitors.

What Metrics Does the Dataset Include?#

Google collects data separately for mobile, tablet, and desktop. CrUX includes information on Core Web Vitals metrics, which comprise these basic metrics:

• Largest Contentful Paint (LCP)
• Interaction to Next Paint (INP)
• Cumulative Layout Shift (CLS)

Core Web Vitals Metrics: the most fundamental of all web speed metrics.

Additional available values in the dataset are examined below.

Origin vs. URL: Data Granularity#

The Chrome UX Report provides data for two page levels. Understanding the difference is key for correct interpretation:

• Origin (e.g., https://www.example.com) returns aggregated data across the entire site, including all subpaths and localizations (/en-us, /fr, /product/…). Origin gives an overview of the entire domain.
• URL (e.g., https://www.example.com/en-us) returns data only for this specific URL. It does not include subpages (/en-us/product/abc).

To group URLs by pattern, use Google Search Console, which handles its own URL groupings.

In practice, you may encounter situations where CrUX data is missing, typically for three reasons:

1. Insufficient Traffic
   Without ~10–15 thousand PV per month, data won't appear in CrUX. Either for the entire domain or for a specific URL.
2. noindex on Homepage
   If the homepage is marked noindex, CrUX origin data won't be reported.
3. Redirect from the Root Page
   If the root automatically redirects to a subpage (e.g., domain.com to domain.com/welcome) and the original root has noindex, CrUX respects the original noindex and may not follow the redirect. Result: origin data disappears, even if /welcome itself is fine.

Advanced Metrics and Navigation Types#

Today, CrUX offers more than just the three Core Web Vitals metrics. Of the advanced data, we frequently use these:

• RTT (Roundtrip Time) separates the backend's impact from the network's. If you have a high RTT but reasonable TTFB, it's the user's connection to the server that's slow, suggesting a CDN might be worthwhile.
• LCP Image Subparts show where time is lost in the LCP image. By breaking it down into server delay, download time, and rendering, you can easily identify whether a better backend, a smaller image, or fetchpriority will help.
• LCP Resource Type distinguishes whether the LCP is an image or text/webfont, guiding where to direct optimization. Either preload the image or the critical font.
• Navigation Types show the share of each navigation type. Increasing the share of BFcache and prerender via Speculation Rules shifts LCP and INP values towards zero since "instant" navigations count as fast in CrUX.

Development of navigation types allows us to see the share of fast or instant navigations.

We've implemented Speculation Rules in practice at PageSpeed.ONE for Innogy, where the growing share of instant navigations significantly improves values for the entire domain. The recipe for keeping the INP metric under control can be found in INP optimization.

Data Latency in CrUX#

Data in the Chrome UX Report is not real-time. Data enters CrUX with a delay of up to a month from the end of the reporting period, depending on the dataset:

• Monthly Dataset (CrUX BigQuery) is published on a fixed day (e.g., the second Tuesday of the month) and contains data for the previous calendar month.
• CrUX Daily is more current. Today you'll see data from yesterday. However, it uses a 28-day window with a rolling end.

Where Can You Find Data from the Chrome UX Report?#

Several tools work with CrUX data, differing in timeliness, metric support, and clarity. In practice, we recommend starting with our website speed test (Insights). You'll get an intuitive UI, PageSpeed.ONE score (SPS) as a single summary number, CrUX data development over time, and synth and CrUX data integration in one dashboard:

Other options for obtaining CrUX data include:

• CrUX Vis is an experimental Google tool for visualizing CrUX. It's more suited for specialists seeking flexibility over clarity.
• PageSpeed Insights from Google shows data but doesn't provide historical development. It's fine for one-off checks but not for monitoring trends.
• Google BigQuery provides raw datasets for advanced SQL analysis. There's also a CrUX History API, offering weekly data faster than ad-hoc BigQuery queries.

How We Use CrUX Data in PageSpeed.ONE Monitoring#

CrUX data reports from monitoring PLUS by PageSpeed.ONE display, for example, metric statuses on a dashboard and value developments on domains:

Speed development according to CrUX data in PageSpeed.ONE speed monitoring.

Monitoring CrUX data is crucial for all sites that have this data. In our Domain Report, you'll find among other things:

• Core Web Vitals metrics (LCP, INP, CLS).
• Additional speed metrics (FCP, TTFB, RTT).
• User segmentation by device type (mobile, tablet, desktop).
• Breakdown of page load methods (navigate, reload, bfcache, prerender…).
• LCP metric resource type (image vs. text).
• Reasons for delays in images that are LCP elements.
• Development of these data over days and months.

Together, this information paints a picture of how your users truly experience web speed and where there's room for improvement. If you prefer to track a single summary number instead of individual metrics, we recommend the PageSpeed.ONE score (SPS), which is based on CrUX data and considers the entire user distribution, not just the 75th percentile.