Timeline of web vitals

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This is a timeline of web vitals, a set of metrics championed by Google that relate to how well web pages load. Of particular interest are three metrics Google calls core web vitals, whose values in field data are used to inform a "page experience" score that affects search ranking on mobile devices.

List of web vitals and corresponding aspects of performance

Note that for the three web vitals measured in both field and Lab data, the thresholds for good and poor for field data match the thresholds for good and poor on Lab data (measured using Lighthouse) respectively. The desktop Lab data thresholds differ for some web vitals, and are not in the table below to keep it simple.

Web vital Aspect of performance Core web vital? Reported in field data (PageSpeed Insights, CrUX report)? Reported in Lab data (Lighthouse, PageSpeed Insights)? Reported in WebPageTest web vitals?[1][2] Threshold for "good" on field data (if applicable) and mobile Lab data (if applicable) (in milliseconds except CLS that is unitless) Threshold for "poor" on field data (if applicable) and mobile Lab data (if applicable) (in milliseconds except CLS that is unitless)
First Contentful Paint (FCP) Loading speed No Yes Yes Not online, but supported in code 1,800 (increased from 1,000 in Lighthouse v8) 3,000
Largest Contentful Paint (LCP) Loading speed Yes Yes Yes (since v6) Yes 2,500 4,000
Speed Index (SI) Loading speed No No Yes (some variant since v2) No 3,400 5,8000
Time to Interactive (TTI) Loading speed, interactivity/responsiveness No No Yes (since at least v5, some variant since v2) Not online, but supported in code 3,800 7,300
Total Blocking Time (TBT) Interactivity/responsiveness No No Yes (since v6) Yes 200 600
First Input Delay (FID) Interactivity/responsiveness Yes Yes No No 100 300
Cumulative Layout Shift (CLS) Visual stability Yes Yes Yes Yes 0.1 0.25

Full timeline

Year Month and date (if available) Event type Type of tool, entity, or change Aspect of performance (specific metrics in parentheses) Type of measurement (field data (from real users) or Lab data (from a bot)?) Event
2010 New product Public diagnostic tool, optimization software Loading speed Lab data Google introduces Google PageSpeed Tools, a suite of tools to help websites understand and improve the speed of their webpages. One of these tools, PageSpeed Insights, would later be a key place where web vitals could be checked for any url.[3]
2012 April 26 Documentation commit Web standard Detailed timing information Field data, Lab data The first commit is made to the repository with the specification for the Resource Timing API. The API allows for access to information on the fetching of the root document and its loading in the browser.[4]
2013 April 9 Documentation commit Web standard Detailed timing information Field data, Lab data The first commit is made to the repository with the specification for the Resource Timing API. The API allows for access to information on the timing of download of various resources.[5]
2016 January 15 Code commit Public diagnostic tool Loading speed, interactivity/responsiveness Lab data The first code commit to the Google Lighthouse GitHub repository is on this date.[6]
2016 June 30 Release Public diagnostic tool Loading speed, interactivity/responsiveness Lab data The Lighthouse v1.0.3 tag is created, suggesting the official release of Lighthouse 1.0.[7]
2016 September 14 Documentation comomit Web standard Loading speed (FCP) Field data, Lab data The first commit is made to the repository documenting the Paint Timing API. This API is used to calculate metrics such as the First Contentful Paint (FCP).[8] Initially supported only on Chromium browsers, the Paint Timing API would eventually be supported by Firefox (Gecko) and Safari (WebKit) as well.[9]
2017 February 1 Data collection Public dataset Loading speed Lab data Data for the HTTP Archive's Loading Speed dataset is available starting this day.[10]
2017 August 24 New version Public diagnostic tool Loading speed, interactivity/responsiveness Lab data Lighthouse v2.0.0 is released. The last commit for it is from May 19. At this point, the Performance section of Lighthouse has the following metrics: First meaningful paint, First interactive (beta), Consistenly interactive (beta), Perceptual Speed Index, and Estimated Input Latency.[11]
2017 October 1 Data collection Public dataset All Field data Data for the Chrome User Experience (CrUX) report, collected anonymously from Chrome users who have consented to the anonymous data collection, is available in a BigQuery dataset starting this day.[12]
2018 July 11 New version Public diagnostic tool Loading speed, interactivity/responsiveness Lab data Lighthouse v3.0.0 is released. The last commit for it is from June 28. This release includes changes to performance weights and scoring thresholds.[13]
2019 January 16 New version Public diagnostic tool Loading speed, interactivity/responsiveness Lab data Lighthouse v4.0.0 is released. The last commmit for it is from January 15.[14]
2019 May 7 New version Public diagnostic tool Loading speed, interactivity/responsiveness Lab data Lighthouse v5.0.0 is released.[15] The metrics used in the performance score, with weights, are: First Contentful Paint (FCP) (23%), Speed Index (SI) (27%), First Meaningful Paint (FMP) (7%), Time To Interactive (TTI) (33%), First CPU Idle (FCI) (13%), and Max Potential FID (0%).[16]
2019 May 13 Documentation commit Web standard Visual stability (CLS) Field data, Lab data The first commit to the GitHub repository for the Layout Instability API is made on this day. This is a proposal by Google for adoption as a web standard, though as of June 2021 it has not been adopted and is only used on Blink-based browsers, which is effectively just Chromium browsers (mainly Chrome, Edge, and Opera).[17]
2019 May 15 Documentation commit Web standard Loading speed (LCP) Field data, Lab data The first commit to the GitHub repository for the Largest Contentful Paint API is made on this day. This is a proposal by Google for adoption as a web standard, though as of June 2021 it has not been adopted and is only used on Blink-based browsers, which is effectively just Chrome browsers (mainly Chrome, Edge, and Opera).[18]
2019 June 11 Announcement Metric introduction Visual stability (CLS) Field data, Lab data The blo post "Cumulative Layout Shift (CLS)" is published on web.dev. In the post, Google describes a new metric, Cumulative Layout Shift (CLS), that measures the totality of unexpected shifts during the lifecycle of a page. This builds upon the Layout Instability API that Google started workingg on recently.[19]
2019 August 8 Announcement Metric introduction Loading speed (LCP) Field data, Lab data The blog post "Largest Contentful Paint (LCP)" is published on web.dev. In the post, Google describes a new metric, Largest Contentful Paint (LCP), that measures how long it takes for the page's main content to have loaded.[20]
2019 September 19 Insight Public diangostic tool All Lab data The page "Lighthouse performance scoring" gives insight into how Google Lighthouse scores are calculated. In particular, it explains that the log-normal distribution used for translating each of the web vitals into a score component is based on real website performance data on HTTP Archive.[21]
2020 April 30 Announcement Metric selection, thresholds All Field data, Lab data Google announces the selection of three of its metrics as core web vitals: Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS). The post also states that the 75th percentile of fielld data should be used for any assessment using web vitals, and specifies thresholds for good and poor values for each of the core web vitals.[22]
2020 May 5 Insight All Field data, Lab data Google publishes three blog posts, one for each of the three core web vitals (LCP, FID, and CLS), on strategies to optimize that core web vital.[23][24][25]
2020 May 12 New version Public diagnostic tool All Lab data In version 21.07, WebPageTest adds support for web vitals. WebPageTest, available at webpagetest.org, is a tool that can be used to report performance data on any web page.[26]
2020 May 19 New version Public diagnostic tool All Lab data Lighthouse v6.0.0 is released (it is expected to ship in the DevTools of Chrome 84, that releases July 14).[27] The performance scoring is updated, with three new metrics added: Largest Contentful Paint (LCP), Total Blocking Time (TBT), and Cumulative Layout Shift (CLS); two of which are among Google's three core web vitals. Three metrics from Lighthouse v5 are removed: First Meaningful Paint, First CPU Idle, and Max Potential FID. The weights are as follows: First Contentful Paint (FCP) (15%), Speed Index (SI) (15%), Largest Contentful Paint (LCP) (25%), Time To Interactive (TTI) (15%), Total Blocking Time (TBT) (25%), and Cumulative Layout Shift (CLS) (5%). This is the first time that Lab data includes a metric for visual stability (the specific metric being CLS).[16]
2020 May 21 Insight Thresholds All Field data In a lengthy blog post, Google describes how it decided on the 75th percentile of field data as the point to use for assessing each of its metrics, and also explains how thresholds were selected for each of the threee core web vitals: LCP, FID, and CLS. The decision for each metric is made by a combination of acceeptable user experience and achievability by webpages with current technology.[28]
2020 May 28 Announcement Search algorithm update All Field data Google announces that at some point in the future, it will start using "page experience" as a ranking factor in search. The page experience signal combines core web vitals, mobile usability, security issues, whether the site is HTTPS, and no intrusive intersitials.[29][30]
2020 June 24 Implementation Web standard Loading speed (FCP) N/A A blog post on the Wikimedia Foundation's tech blog describes work donee by Wikimedia Foundation engineers to implement the Paint Timing API in WebKit, the engine used by Safari, thus making it available in future versions of Safari.[31]
2020 November 10 Announcement Search algorithm update All Field data Google announces that it will start using "page experience" as a ranking factor for mobile searches starting May 2021. The page experience signal combines core web vitals, mobile usability, security issues, whether the site is HTTPS, and no intrusive interstitials.[32][33]
2020 December 17 New version Public diagnostic tool All Lab data Lighthouse v7.0.0 is released. It is expected to be shipped with Chrome 89 (released March 2, 2021) and becoms part of PageSpeed Insights on February 19, 2021.[34]
2021 February 17 Release Threshold update All Field data Field data available in Google Search Console and PageSpeed Insights are updated to consider a metric value at a threshold as being on the good side of the threshold. For instance, for CLS, the the threshold for good CLS is 0.1; a 75th percentile CLS value of exactly 0.1 would now be considered good.[35]
2021 April 7 Announcement Metric definition update Visual stability (CLS) Field data, Lab data Google announces a planned update to the calculation of Cumulative Layout Shift (CLS) to be fairer to long-lived pages. The update changes the definition of CLS to look at the largest CLS over 5-second windows with a 1-second gap. The rollout of this definition update would happen in June.[36][37]
2021 April 19 Release Private diagnostic tool All Field data A new section called "Page experience on mobile" is added to Google Search Console (where people can access this data for their own sites only). This is restriced to mobile searches; it reports on the percentage of urls and number of search impressions that have "good page experience" i.e., that perform well on core web vitals, mobile usability, security issues, whether the site is HTTPS, and ads experience.[38]
2021 April Insight Data All Lab data Searchmetrics publishes a study of core web vitals, looking at Lab data for over 2 million URLs on two of the three core web vitals (LCP and CLS) and a proxy for the third core web vital (using Total Blocking Time (TBT) instead of FID). YouTube is highlighted as an outlier that skews measurement.[39]
2021 April 19 Announcement Search algorithm update All Field data Google announces an updated timeline of mid-June to August for its rollout of page experience as a ranking factor for mobile searches. The previous announced rollout time was May 2021; the time extension is allegedly to give websites more time to prepare.[40]
2021 May 4 Insight Cross-browser comparison of metric definition Loading speed (FCP) N/A A blog post on the WebPageTest blog describes challenggs with comparing First Contentful Paint (FCP) across browsers. FCP is one of the first web vitals to be available across all major browsers with the release of Safari 14.1.[9]
2021 June 1  – 2, some changes a little later in June Release Metric definition update Visual stability (CLS) Field data Google updates its field data tools including the Chrome User Experience (CrUX) report, PageSpeed Insights, and Google Search Console, to use an updated definition of Cumulative Layout Shift (CLS) that looks at the largest CLS over 5-second windows with a 1-second gap. The planned change itself had been announced back in April, but it had not yet been reflected in the tools Google used to report on field data, as well as in Google's Lighthouse tool available on PageSpeed Insights and in Chrome Developer Tools (canary channel only, so not part of officially released Chrome yet).[41][42][43]
2021 early June Release Metric definition update Loading speed (LCP) Field data Some changes are made to LCP calculations to account for offscreen images and multiple images of the same size.[44]
2021 June 2 New version Public diagnostic tool All Lab data Lighthouse v8.0.0 is released. The release is made available on PageSpeed Insights immediately, and is expected to ship as part of Chrome 93. This includes Lab-side changes corresponding to field data updates for CLS released at around the same time; it also includes threshold changes for TBT and FCP and a reweighting: FCP: 15% to 10%, SI: 15% to 10%, TTI: 15% to 10%, TBT: 25% to 30%, and CLS: 5% to 15%. A new diagnostic aide called the Lighthouse Treemap is also released.[45][46]
2021 June 15  – end of August Release Search algorithm update All Field data The rollout of Google's "page experience on mobile" update happens during this period. The update is limited to mobile searches, and gives weight to a "page experience" factor that includes performance on core web vitals, mobile usability, security issues, whether the site is HTTPS, and ads experience.[47][48]

See also

References

  1. ↑ "RunResultHtmlTable.php". Retrieved July 7, 2021. 
  2. ↑ "Web page performance test result for www.example.com/". July 7, 2021. Retrieved July 7, 2021. 
  3. ↑ Ram, Ramani (2011-07-29). "Page Speed Service: Web performance, delivered". googlecode.blogspot.com/. Retrieved 17 March 2015. 
  4. ↑ "Performance Timeline - Removed Section 4.4. Navigation Timing 2 - Added PerformanceNavigationTiming interface". April 26, 2012. Retrieved July 7, 2021. 
  5. ↑ "Initial draft of Resource Timing L2 spec.". April 9, 2013. Retrieved July 7, 2021. 
  6. ↑ Lewis, Paul (January 15, 2016). "Adds tests.". Retrieved July 7, 2021. 
  7. ↑ Irish, Paul (June 30, 2016). "Lighthouse v1.0.3". Retrieved June 18, 2021. 
  8. ↑ "Initial commit". September 14, 2016. Retrieved July 7, 2021. 
  9. ↑ 9.0 9.1 "Why First Contentful Paint Doesn't Work As a Cross-Browser Metric". WebPageTest Blog by Catchpoint. May 4, 2021. Retrieved July 7, 2021. 
  10. ↑ "Report: Loading Speed". Retrieved June 19, 2021. 
  11. ↑ "Lighthouse v2.0.0". August 24, 2017. Retrieved June 19, 2021. 
  12. ↑ "Report: CrUX". Retrieved June 19, 2021. 
  13. ↑ "Lighthouse v3.0.0". July 11, 2018. Retrieved June 19, 2021. 
  14. ↑ "Lighthouse v4.0.0". January 16, 2019. Retrieved June 19, 2021. 
  15. ↑ "Lighthouse v5.0.0". May 7, 2019. Retrieved June 19, 2021. 
  16. ↑ 16.0 16.1 Clark, Connor (May 19, 2020). "What's New in Lighthouse 6.0. New metrics, Performance score update, new audits, and more.". Retrieved June 19, 2021. 
  17. ↑ "Create README.md". May 13, 2019. Retrieved June 19, 2021. 
  18. ↑ "initial commit". May 15, 2019. Retrieved June 19, 2021. 
  19. ↑ Walton, Philip; Mihajlija, Milica (June 11, 2019). "Cumulative Layout Shift (CLS)". Retrieved June 19, 2021. 
  20. ↑ Walton, Philip (August 8, 2019). "Largest Contentful Paint (LCP)". Retrieved June 19, 2021. 
  21. ↑ "Lighthouse performance scoring: How Lighthouse calculates your overall Performance score". September 19, 2019. Retrieved June 19, 2021. 
  22. ↑ Walton, Philip (April 30, 2020). "Web Vitals". Retrieved June 19, 2021. 
  23. ↑ Djirdeh, Houssein (May 5, 2020). "Optimize Largest Contentful Paint. How to render your main content faster.". Retrieved June 19, 2021. 
  24. ↑ Djirdeh, Houssein; Osmani, Addy (May 5, 2020). "Optimize First Input Delay. How to respond faster to user interactions.". Retrieved June 19, 2021. 
  25. ↑ Osmani, Addy (May 5, 2020). "Optimize Cumulative Layout Shift. Learn how to avoid sudden layout shifts to improve user-experience". Retrieved June 19, 2021. 
  26. ↑ "Added the web vitals measurements". May 12, 2020. Retrieved July 7, 2021. 
  27. ↑ "Lighthouse v6.0.0". May 19, 2020. Retrieved June 19, 2021. 
  28. ↑ McQuade, Bryan (May 21, 2020). "Defining the Core Web Vitals metrics thresholds. The research and methodology behind Core Web Vitals thresholds". Retrieved June 19, 2020. 
  29. ↑ "Evaluating page experience for a better web". Google Search Central. May 28, 2020. Retrieved June 19, 2021. 
  30. ↑ Schwartz, Barry (May 28, 2020). "The Google Page Experience Update: User experience to become a Google ranking factor. Core Web Vitals metrics will start to impact rankings in 2021. Here is what you need to know.". Search Engine Land. Retrieved June 19, 2021. 
  31. ↑ Rosenthal, Noam; Dubuc, Gilles (June 24, 2020). "How we contributed Paint Timing API to WebKit". Retrieved July 7, 2021. 
  32. ↑ "Timing for bringing page experience to Google Search". Google Search Central. November 10, 2020. Retrieved June 19, 2021. 
  33. ↑ Schwartz, Barry (November 10, 2020). "Google Page Experience Update to launch May 2021 with new labels in search results. Google will highlight search results that have a great page experience.". Search Engine Land. Retrieved June 19, 2021. 
  34. ↑ "Lighthouse v7.0.0". December 17, 2020. Retrieved Jun 19, 2021. 
  35. ↑ Schwartz, Barry (February 18, 2021). "Google updated metric boundaries for core web vitals in Search Console. You may see more green scores in your core web vitals report in Search Console.". Search Engine Land. Retrieved June 19, 2021. 
  36. ↑ Sullivan, Annie; Song, Hongbo (April 7, 2021). "Evolving the CLS metric. Plans for improving the CLS metric to be more fair to long-lived pages.". Retrieved June 19, 2021. 
  37. ↑ Kadlec, Tim (April 13, 2021). "Diving Into the New Cumulative Layout Shift". WebPageTest blog by Catchpoint. Retrieved July 7, 2021. 
  38. ↑ Schwartz, Barry (April 19, 2021). "Google Search Console adds Page Experience report and filters for Search Performance report. These new reports give us more information to prepare for the new timeline for the page experience update rollout.". Search Engine Land. Retrieved June 19, 2021. 
  39. ↑ "CORE WEB VITALS Study – April 2021" (PDF). Searchmetrics. Retrieved June 19, 2021. 
  40. ↑ Schwartz, Barry (April 19, 2021). "Google postpones page experience update rollout. The page experience update will now gradually rollout in mid-June and won't be fully live until the end of August.". Search Engine Land. Retrieved June 19, 2021. 
  41. ↑ Osmani, Addy; Sweeny, Elizabeth (June 2, 2021). "Evolving Cumulative Layout Shift in web tooling". Google. Retrieved June 19, 2021. 
  42. ↑ "Data anomalies in Search Console". June 1, 2021. Retrieved June 19, 2021. 
  43. ↑ Schwartz, Barry (June 2, 2021). "Updated Cumulative Layout Shift Metric Is Live In Google Search Console". Search Engine Roundtable. Retrieved June 19, 2021. 
  44. ↑ "How big and fast was this Google June 2021 core update?; Wednesday's daily brief. Google cuts short names from Google My Business". June 9, 2021. Retrieved June 19, 2021. 
  45. ↑ "Lighthouse v8.0.0". June 2, 2021. Retrieved June 19, 2021. 
  46. ↑ "Lighthouse Scoring Calculator". Retrieved June 19, 2021. 
  47. ↑ "The page experience update is now slowly rolling out (Top Stories will begin using this new signal by Thursday). It will be complete by the end of August 2021.". June 15, 2021. Retrieved June 18, 2021. 
  48. ↑ Schwartz, Barry (June 15, 2021). "Google page experience update now slowly rolling out. Top stories will stop using AMP as an eligibility factor starting Thursday.". Search Engine Land. Retrieved June 18, 2021. 
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