Timeline of web vitals

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The timeline currently offers focused coverage of the period until February 2024. It is likely to miss important developments outside this period (particularly after this period) though it may have a few events from after this period.

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 within Google.

Big picture

Time period Development summary
2007 – 2015 This period sees the emergence of diagnostic tools and web standards that help diagnose page load speed. This is also the period where some initial concepts such as "speed index" and "performance budgets" start getting fleshed out.
2016 – 2018 This period sees the emergence of systematic datasets covering web performance for a wide range of websites, including the HTTP Archive (that uses Lab data) and the Chrome User Expeience Report (CrUX) that uses field data collected anonymously from Chrome users. It also sees the growth of public diagnostic tools for site performance, including Lighthouse, that is integrated into Chrome's Developer Tools.
2019 This is the year when Google starts getting more directly involved with improving site performance, with communication being done via a bunch of blog posts on web.dev. During this year, the understanding of site performance is expanded to include visual stability (epitomized by Cumulative Layout Shift (CLS)). Previously the focus had been on loading speed and interactivity/responsiveness.
2020 This is the year that Google officially announces three "core web vitals": Largest Contentful Paint (LCP) for loading speed, Cumulative Layout Shift (CLS) for visual stability, and First Input Delay (FID) for interactivity/responsiveness. Google also provides guidance that the 75th percentile field data values for these metrics will be used to influence search results on mobile and desktop in the coming years. In particular, Google clarifies its focus on "field data" (as collected by the CrUX report) as the data it uses for official evaluation, and clarifies the role of Lab data as an aid for self-diagnosis by people involved with developing websites. The potential of core web vitals to affect search results leads to a flurry of activity in the SEO community. A number of new diagnostic tools and data sources emerge, both from Google and from the rest of the ecosystem, and existing tools on site performance shift direction a little bit to start focusing on core web vitals.
2021 – 2022 During this period, Google starts using core web vitals to influence search results, with mobile search results being affected starting mid-2021 and desktop search results being affected starting early 2022. However, the magnitude of impact on search results is small, leading to a dying down of activity and attention to core web vitals in the SEO community. Nonetheless, the overall proportion of origins passing on the core web vitals continues to improve over the period, with CLS (one of the more actionable core web vitals) seeing the most dramatic improvement. The improvements in the case of CLS are due to a combination of definition changes and websites making improvements. The less dramatic improvement for LCP is due to a combination of Chrome browser speed updates, computers getting a litle faster over time, and websites making improvements.

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. This has been the case since June 2021 updates to field data thresholds and the corresponding release of Lighthouse v8. 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)
Time to First Byte (TTFB) Loading speed No Yes No No 800 1,800
First Contentful Paint (FCP) Loading speed No Yes Yes Not online, but supported in code 1,800 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 No (retired in v10; was reported until v9 and 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 (but set to retire March 2024) Yes No No 100 300
Interaction to Next Paint (INP) Interactivity/responsiveness No (but set to become one in March 2024) Yes No No 200 500
Cumulative Layout Shift (CLS) Visual stability Yes Yes Yes Yes 0.1 0.25

Numerical and visual data

The table below is based on monthly summaries provided in the CrUX announce mailing list.[3] Note that the total number of origins is not necessarily the denominator for the percentages; individual percentages have as denominator only the number of origins for which there was sufficient data for that particular metric.[4]

Year and month (YYYY-MM) Number of origins covered in dataset Percentage good Largest Contentful Paint (LCP) Percentage good First Input Delay (FID) -- replaced by INP as a core web vital in March 2024 Percentage good Cumulative Layout Shift (CLS) Percentage good on all core web vitals Percentage good on Interaction to Next Paint (INP) -- becomes a core web vital in March 2024 Percentage good on CLS, LCP, and INP (the set of core web vitals starting March 2024) Special notes
2020-05 7,103,486 46 86 64 27 Corrected data to restrict denominator[4]
2020-06 7,501,835 47.84 86.74 57.45 25.34
2020-07 7,527,878 47.6 86.9 57.2 25.2
2020-08 7,773,359 47.1 86.9 57.1 24.9 Bump in origin coverage due to a data pipeline change that now accepts all user experiences with a FCP[5]
2020-09 7,937,088 46.8 87.6 55.8 24.6
2020-10 8,050,755 47.0 88.2 52.3 23.7
2020-11 7,942,408 47.0 88.8 51.1 23.5
2020-12 7,629,156 47.1 88.7 51.0 23.4
2021-01 8,185,540 47.81 89.28 50.25 23.71
2021-02 8,264,371 47.99 89.46 45.99 21.98
2021-03 8,326,310 49.01 89.66 51.84 24.81
2021-04 8,423,302 49.4 89.8 53.8 25.8
2021-05 8,411,670 50.7 89.9 60.4 29.2 Metric definition updates released in early June are applied to this data, including the 5-second session window for CLS, and at least partly explains the sharp increase in the percentage of origins with good CLS.[6]
2021-06 8,416,608 50.6 93.0 61.0 30.6 The effect of the double-tap-to-zoom FID metric change in Chrome 91, that improves measured FID, is largely seen in this month, and at least partly explains the sharp increase in the percentage of origins with good FID.[7]
2021-07 8,174,923 50.0 93.2 61.2 30.4
2021-08 8,431,699 50.9 93.2 62.1 31.3
2021-09 8,660,068 50.9 93.3 65.4 32.8
2021-10 8,784,894 50.0 93.4 65.9 34.1 This is the first month when the percentages reported are based on the "optional FID" methodology adopted in PageSpeed Insights on June 10, 2021.[8][9]
2021-11 8,733,078 50.8 93.5 66.1 34.8 The uncapped CLS metric (that was the old way of calculating CLS before a definition change around May/June) is retired from the BigQuery dataset starting with this month.[10]
2021-12 8,398,796 51.1 93.3 66.1 35.0
2022-01 8,934,350 52.4 93.9 68.9 37.6
2022-02 8,764,246 52.7 94.9 70.6 39.0 This is the first month for which the dataset includes data on the experimental responsiveness metric that had been described by Google in blog posts in 2021.[11]
2022-03 8,555,307 53.4 94.9 70.6 39.6
2022-04 8,602,902 55.2 94.9 71.6 41.2 This is the first month for which the dataset includes data on a new experimental metric called Interaction to Next Paint (INP), a new variant of the experimental responsiveness metric.[12]
2022-05 11,024,795 56.5 94.7 71.7 42.0 This is the first month where effective connection type and form factor fields transition from required fields to optional fields in the CruX dataset, resulting in more eligible traffic data for websites, and therefore a larger number of origins with enough traffic to qualify for inclusion in the CrUX report. A bug resulted in this change not having its full effect (on increase in origin coverage) in this month; the full effect is expected to be seen in June. Also, the LCP improvement is attributed to an increase in Chrome's speed on Android devices, "thanks to prioritizing critical navigation moments on the browser user interface thread."[13]
2022-06 16,230,572 54.9 94.3 72.3 41.3 There is a significant increase in the number of origins compared to last month and even more so compared to two months ago, the increase over the past two months is due to making form factor and effective connection type optional. Due to the increase in coverage of low-traffic origins, the numbers aren't directly comparable with previous months; in particular, the seeming decline in LCP is mostly a result of the expanded coverage. Restricting to the top 1,000 or top 10,000 origins shows a clearer trend of continued improvement.[14]
2022-07 16,190,453 54.3 94.2 71.7 40.6 This release includes a change which records the CLS metric at the first OnHidden in addition to tab close. Also, there is a bug in the origin filtering causing a small number of origins to be incorrectly filtered from the release.[15]
2022-08 16,754,655 53.7 94.2 72.5 40.7 This release continues to partially have the bug in the previous release due to which some origins are missed; the number of origins missed is smaller than last time but still not zero.[16]
2022-09 17,715,277 54.5 94.8 72.4 41.4
2022-10 17,637,195 54.8 95.0 72.3 41.6 This release includes a breakdown of "rank" popularity for top 5,000 sites, top 50,000 sites, etc. in addition to the already-existing rank popularity for top 1,000 sites, top 10,000 sites etc.[17]
2022-11 17,618,944 54.9 95.1 72.4 41.8
2022-12 16,824,271 54.8 95.0 72.7 41.8
2023-01 18,200,000 56.2 95.2 73.1 43.0
2023-02 18,184,396 56.3 95.3 73.1 43.1
2023-03 18,495,210 57.7 95.5 73.4 44.2
2023-04 18,406,973 57.1 95.3 72.9 43.5 This month sees a slight decrease in FCP and LCP pass rates. The FCP pass rate decrease is attributed to a paint timing fix in Chrome 109. The LCP pass rate decrease is attributed to a change to exclude low-entropy images introduced on April 6 and also, to a lesser extent, the paint timing change.[18]
2023-05 18,377,791 56.8 95.5 73.3 43.6 This month sees a slight decrease in FCP and LCP pass rates. The FCP pass rate decrease is attributed to a paint timing fix in Chrome 109. The LCP pass rate decrease is attributed to a change to exclude low-entropy images introduced on April 6 and also, to a lesser extent, the paint timing change.[19]
2023-06 18,065,718 57.2 95.6 73.7 44.1 77.7 The data for this month includes partial resolution of the "root page redirect issue" where some origins that redirect their root page are excluded from CrUX. This is also the first month where the INP metric is included without the experimental prefix (it's also included with the experimental prefix for backward compatibility). This is in preparation for INP becoming a core web vital in March 2024.[20]
2023-07 17,976,663 57.8 95.7 73.8 44.6 77.8 The data for this month is after full resolution of the "root page redirect issue" where some origins that redirect their root page are excluded from CrUX.[21]
2023-08 18,263,523 58.3 95.8 74.4 45.3 77.6 41.6 The data for this month includes the partial impact of several Chrome improvements affecting CLS and LCP, with the effect generally positive.[22][23][24]
2023-09 18,405,462 58.5 95.8 74.7 45.7 78.0 42.1 The improvements introduced in the previous month, that continued to roll out this month, are likely responsible for continued improvements to LCP and CLS, despite slight downturns in FCP and TTFB.[25]
2023-10 18,383,750 59.4 95.8 75.9 46.9 78.7 43.4 The final rollout of the improvements introduced in August, that continued to roll out this month, are likely responsible for continued improvements to LCP and CLS.[26]
2023-11 18,265,721 59.8 96.0 76.2 47.4 79.2 43.9
2023-12 17,323,447 60.4 95.9 76.4 48.0 79.0 44.4
2024-01 18,583,729 61.6 96.2 76.4 49.0 80.7 45.8

Full timeline

Inclusion criteria

The following are some kinds of events that qualify for inclusion in the timeline:

  • Launch of new private or public diagnostics tools related to web vitals, or major updates to such tools
  • Major version updates to Lighthouse, the main Lab data tool
  • Introduction of a new web vital metric, changes to the definition of a web vital metric, or addition or removal of a web vital from the list of core web vitals
  • Changes to browser behavior that could affect the data for one or more web vitals
  • Blog posts or articles with insight around how to improve on web vitals, or critical discussion of web vitals and how much importance to give to them
  • Important conferences about site performance (such as the performance.now() conference)

Here are some examples of things that will not qualify for this timeline:

  • Minor version updates to Lighthouse
  • Performance trajectories of specific websites, except to the extent that the analysis of such performance qualifies as valuable insight into web vitals
  • Individual talks at a conference (such as the performance.now() conference) unless the specific talk breaks a lot of new ground and gets a bunch of commentary; in many cases, talks at these conferences summarize past discussion so the original post or articles for such discussions should be included instead

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; aka Real User Monitoring (RUM)) or Lab data (from a bot or synthetic local testing))? Event
2007 July New product Public diagnostic tool Loading speed Lab data Yahoo! launches YSlow, a Firefox add-on built on top of Firebug, to help debug speed issues on websites.[27][28] YSlow operationalilzes Yahoo! Chief Performance Officer Steve Souders' 13 rules for high-performance web sites (also covered in his book "High Performance Web Sites").[29] Development on it would cease after 2014 as people migrated to other tools like Google's Page Speed, Webpagetest, and later Lighthouse.[30][31]
2009 June 5 New product Public diagnostic tool Loading speed Lab data Google releases Page Speed, a Firefox add-on built on top of Firebug, to help debug speed issues on websites. Commentators consider this to be Google's equivaent to Yahoo's YSlow tool.[32]
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 Navigation Timing API. The API allows for access to information on the fetching of the root document and its loading in the browser.[33]
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.[34]
2014 September 29 Documentation commit Web standard Loading speed (Speed Index) Field data The first commit is made to the repository with the specification for the RUM Speed Index (RUM stands for real user monitoring), an attempt to calculate a Speed Index based on field data. As of 2021, Speed Index is still calculated in the Lab.[35]
2014 November 18 Insight Metric definition, concept development Loading speed Field data, Lab data Tim Kadlec publishes his landmark post titled "Performance Budget Metrics" that classifies metrics used for performance budgets in four categories: (1) milestone timings (measuring when specific milestones in loading and rendering are achieved), (2) SpeedIndex (measuring how a page loads from start to finish), (3) quantity-based metrics (such as total number of requests, overall page weight, total image weight), and (4) rule-based metrics (such as PageSpeed and YSlow score).[36] Performance budgets would eventually be supported by build tools and diagnostic tools, and would be the subject of further analysis;[37] one analysis on web.dev would use a similar categorization of performance budget metrics (without a separate category for SpeedIndex).[38]
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.[39]
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.[40]
2016 September 14 Documentation commit 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).[41] Initially supported only on Chromium browsers, the Paint Timing API would eventually be supported by Firefox (Gecko) and Safari (WebKit) as well.[42]
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.[43]
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.[44]
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.[45]
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.[46]
2018 August 11 Release Public ranking tool Loading speed, interactivity/responsiveness Lab data The earliest Wayback Machine snapshot of webperf.xyz, a site that maintains a leaderboard of sites based on their performance, is from this date. At launch time, it uses webpagetest.org for its data generation.[47] The tool would be referenced in an Atlantic article on August 23 about their efforts to speed up ad loading on their site.[48]
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.[49]
2019 May 7 New version Public diagnostic tool Loading speed, interactivity/responsiveness Lab data Lighthouse v5.0.0 is released.[50] 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%).[51]
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).[52]
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).[53]
2019 June 11 Announcement Metric introduction Visual stability (CLS) Field data, Lab data The blog 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.[54]
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.[55]
2019 September 19 Insight Public diagnostic 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.[56]
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.[57]
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.[58][59][60]
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.[61]
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).[62] 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).[51]
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.[63]
2020 May 27 Release Private diagnostic tool All Field data Google updates Google Search Console adding a section on core web vitals. This section reports on field data performance on both mobile and desktop on each of the three core web vitals (CLS, LCP, and FID). It is based on the CrUX report. Rather than making all the data available for each url, Search Console groups urls together and reports on aggregate performance of the url groups.[64]
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.[65][66]
2020 June 24 Implementation Web standard Loading speed (FCP) N/A A blog post on the Wikimedia Foundation's tech blog describes work done 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.[67]
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.[68][69]
2020 November 16 New version Public diagnostic tool, private diagnostic tool All Lab data GTmetrix, a performance optimization tool, switches from its legacy Timings and PageSpeed/YSlow measurements to using Lighthouse as its underlying engine; the new data includes Performance and Structure tabs, an overall GTMetrix grade, and a web vitals section that includes LCP, CLS, and Total Blocking Time (TBT).[70][71][72]
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.[73]
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.[74]
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.[75][76]
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.[77]
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.[78]
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.[79]
2021 April 25 New version Public ranking tool All Lab data The backend for webperf.xyz is switched from webpagetest to Lighthouse on this date (or least, this is the earliest date with data recorded using Lighthouse).[80]
2021 May 4 Insight Cross-browser comparison of metric definition Loading speed (FCP) N/A A blog post on the WebPageTest blog describes challenges 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.[42]
2021 May 18 Insight Business impact All Field data (mostly) with some discussion of Lab data In a blog post on web.dev that also includes a video, two Google staff members discuss the business impact of (core) web vitals. The post includes case studies of: Vodafone, iCook, Tokopedia, Redbus, and several others who have improved one or more of the core web vitals and seen improvement in traffic, user engagement, and revenue. These impacts are prior to (and therefore not caused by Google starting to use page experience (including core web vitals) as a signal for search ranking.[81][82]
2021 May 25 New version Browser behavior Interactivity/responsiveness (FID) Field data Chrome 91 disables double-tap-to-zoom when the viewport meta tag specifies width=device-width or initial-scale>=1.0, even when implicitly doing so, like for example in minimum-scale=1.5, maximum-scale=2. Because DTZ negatively impacts FID and the amount of pages where DTZ is disabled is increased, Google expects some sites to see FID improvements.[83]
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).[84][85][86]
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.[87]
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.[88][89]
2021 June 10 New version Public diagnostic tool All, FID Field data PageSpeed Insights field data now reports field data even for pages where some (but not all) of the field data metrics have insufficient data; in such cases, only the metrics with sufficient data are reported.[90] Rick Viscomi further clarifies on Twitter that this will most affect pages missing FID, since FID data tends to be much more likely to be missing than LCP or CLS data. Further, an origin with insufficient FID data will be considered to pass overall in core web vitals if it passes LCP and CLS; however, an origin must have LCP and CLS data in order to be considered passing on core web vitals.[9]
2021 June 15  – September 2 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.[91][92][93]
2021 June 21, November 3 Proposal Metric definition update Interactivity/responsiveness (responsiveness metric) Field data In two blog posts on web.dev. the Chrome Speed team proposes a new responsiveness metric, that is expected to correlate with the Lab data metrics of time to interactive (TTI) and total blocking time (TBT) and whose goal is to measure responsiveness over the page lifecycle. It is expected to overcome some of the shortcoming of first input delay (FID) and be a more holistic measure of responsiveness.[94][95]
2021 June 24 Release Public diagnostic tool All Field data The HTTP Archive's Core Web Vitals Technology Report is released. This builds on the Chrome User Experience Report (CrUX report) as well as the HTTP Archive's data on CMS and technology stacks used by various websites, to provide a big-picture view of performance on core web vitals by CMS and technology stack.[96]
2021 August 17 Insight Search algorithm update All Field data, Lab data A blog post on the Semrush blog reviews the rollout of Google's page experience update. It goes over trends in field data and Lab data performance of mobile urls before and during the rollout, as well as the correlation with mobile search rankings. It detects a small correlation in the expected direction.[97][98]
2021 August 17 Insight Public diagnostic tool, private diagnostic tool All Field data, Lab data A blog post on web.dev describes how field and Lab data differ conceptually, how the values of field data and Lab data might differ in general, and concrete field/Lab differences associated with the three core web vitals.[99]
2021 August 31 New version Browser behavior Visual stability (CLS) Field data Chrome 93 makes changes to its calculation of cumulative layout shift (CLS) to ignore changes to offscreen elements countered with scroll anchoring, as well as layout shifts while dragging or resizing elements with a mouse. This is expected to improve the performance of websites on CLS.[100]
2021 September 16 Insight Search algorithm update All Field data A blog post on the Sistrix blog titled "Core Web Vitals is a Measurable Ranking Factor" documents the observed effect size on ranking of sites passing all core web vitals versus the average and versus sites failing all core web vitals.[101][98]
2021 September 21 New version Browser behavior Loading speed (FCP) Field data, Lab data Chromium is updated so that paint timing is not triggered by content that is not visible due to being under the effect of an opacity: 0 style. This change is part of the Chrome 94 release on September 21, 2021, and is also expected to affect other Chromium-based browsers such as Edge and Opera. The change is expected to increase (worsen) measured FCP (in field and Lab data) for some sites, without directly changing the end user experience.[102]
2021 October 27 Insight Search algorithm update All Field data A post on Search Engine Land describes the relatively minor impact that page experience has had on search rankings so far, as well as SEOs questioning the value of spending time on improving page experience. It also discusses other potential benefits of improving page experience beyond the search ranking impact.[98]
2021 November 3 New version Public diagnostic tool All Field data, Lab data A new version of the PageSpeed Insights UI is released.[103] Around this time (by November 15), PageSpeed Insights is moved to pagespeed.web.dev.[104]
2021 November 13, November 15 New version Public diagnostic tool All Lab data Starting November 13, PageSpeed Insights starts using Lighthouse 9.0.0.[104] On November 15, Lighthouse 9.0.0 is officially released. It is expected to be part of stable Chrome starting Chrome 98. One of the new functionalities it offers is support for user flows, making it easier to run Lighthouse for users with a warm cache, and to carry out user interactions.[105][106][107]
2021 November 16 New version Browser behavior Loading speed (LCP) Field data, Lab data Chrome 96 fixes a bug in LCP calculation where a previous intended change to ignore images occupying the full viewport had been applied incorrectly to iframes to use the iframe's full viewport rather than the page's full viewport.[108]
2021 December 8 Insight Public diagnostic tool All Lab data (with some discussion of field data) In a blog post on Calibre's blog, Karolina Szczur argues against focusing on the Lighthouse performance score. Arguments include: it’s impossible to describe user experience with one metric, Performance Score is relative to device type and speed trends, Performance Score is prone to variability, Performance Score doesn’t make it easier to talk about speed, Performance Score can be gamed, Performance Score doesn’t matter for SEO, and Performance Score has been overtaken by Core Web Vitals.[109]
2021 December 22 Insight Public diagnostic tool, private diagnostic tool Loading speed (LCP) Field data An article in Smashing Magazine describes in detail their efforts to get their core web vital of LCP to a passing state, including their use of tools such as Google Search Console, web-vitals JS library + CrUX dashboard, PageSpeed Insights, and the CrUX BigQuery dataset. The main methods used include the removal of author images from mobile and the skipping of loading webfonts for users with slow connections and/or data-saving preferences.[110]
2022 January 17 Release Private diagnostic tool All Field data The page experience section of Google Search Console, that previously only had "page experience on mobile" data, now has separate data for mobile and desktop. This update is made ahead of the rollout (scheduled for February and March 2022) of page experience on desktop as a search signal on desktop.[111]
2022 January 18 Insight Public diagnostic tool, private diagnostic tool All Field data, Lab data An article on web.dev provides a summary of the various diagnostic tools available for monitoring and debugging web vitals.[112]
2022 February 1 Release Metric definition update Visual stability (CLS) Field data Starting with Chrome 98: "The cumulative layout shift score will be recorded the first time a page moves from the foreground to the background, which can fill in for the layout shift values that are not able to be recorded at tab close, the current CLS reporting point." The change would show up in the CruX BigQuery dataset starting with the July 2022 dataset.[113]
2022 February 10 Insight Business impact All, but concrete examples focused on visual stability (CLS) Field data A sponsored post by Clickio on Search Engine Land makes the case for the importance of optimizing Core Web Vitals, mentioning a few cases involving their customers. The post ends with a plug for Clickio's web vitals monitoring product.[82]
2022 February 22  – March 3 Release Search algorithm update All Field data As previously announced on November 4, 2021, Google executes on the rollout of using page experience as a ranking factor on desktop during this period. Page experience on desktop includes all the core web vitals as well as all the other page experience signals on mobile except mobile-friendliness.[114][115][116]
2022 March 29 Release Public diagnostic tool All Lab data A blog post on the Chrome developer blog announces the Performance insights panel in Chrome Developer Tools. This panel has some of the functionality of the performance panel with a greater orientation toward producing actionable insights. It features diagnostics for each of the core web vitals.[117]
2022 May 6 Proposal Metric definition update Interactivity/responsiveness (Interaction to Next Paint (INP)) Field data (but also available in Lab tools) A blog post on web.dev announces Interaction to Next Paint (INP), a new experimental variant of the responsiveness metric, that may eventually replace First Input Delay (FID).[118]
2022 May 12 Insight All Field data A 2-year anniversary conversation about core web vitals is published to Twitter Spaces. The conversation features Annie Sullivan from Chrome, Barry Pollard, Crystal Carter, and Henri Helvetica.[119]
2022 May 16 Insight Metric definition update Interactivity/responsiveness (Interaction to Next Paint (INP)) Field data A blog post on web.dev looks at field data across a variety of frameworks for the experimental responsiveness metric titled Interaction to Next Paint (INP), and also describes what the frameworks (React, Next.js, and Angular) are doing to improve INP performance.[120]
2022 July 19 Insight Public diagnostic tool All Field data Documentation on the Chrome User Experience (CrUX) report moves to a new home.[121][122]
2022 August 15 Insight All Field data A blog post on web.dev describes various sources of difference between the official CrUX report and real user monitoring (RUM) data collected by websites using JavaScript.[123]
2022 October 27 – 28 Insight All Field data, Lab data The performance.now() 2022 conference is held in Amsterdam over these two days. Talks from the conference would be released on YouTube in the coming days. Many of the talks would be about web vitals both in the field and in the Lab.[124][17]
2022 November 4 Public diagnostic tool All Lab data pagespeed.web.dev is updated to include the entire Lighthouse report, not just the performance section of the report that it previously made available.[125]
2023 January 10 Insight All Field data A blog post on web.dev includes a list of top recommendations to improve core web vitals.[126]
2023 February 7 Release Public diagnostic tool All Field data The CrUX History API is introduced; this API provides access to CrUX data at the level of url and origin for the past 6 months.[127]
2023 February 9 (announcement), ~February 16 and March 29 (rollout) New version Public diagnostic tool All Lab data Lighthouse 10 is announced; this introduces the scoring change of removing Time to Interactive (TTI) from the score calculation. There are a number of other changes to the available audits and the code now ships with full TypeScript declarations. Lighthouse 10 is shipped to PageSpeed Insights in mid-February and releases as part of Chrome 112 with its release on March 29.[128][129]
2023 March 1 New version Browser behavior Loading speed (FCP) Field data Chrome 111 includes two bugfixes: (1) a bug that causes FCP to be reported as smaller (better) than it actually is gets fixed, so that the actual FCP now represents the more pessimistic true value, (2) a bug that causes the actual FCP event to sometimes get unnecessarily delayed is fixed. The net effect of these changes is that reported FCP increases (gets worse) but actual FCP decreases (gets better).[130] This would be cited as a reason for the decrease in FCP and LCP pass rates in the CrUX mailing list announcements for April 2023[18] and May 2023.[19]
2023 April 6 New version Browser behavior Loading speed (LCP) Field data A change is introduced to Chrome to exclude low-entropy images from the pool of candidates for the LCP image. This could affect measured LCP if the low-entropy image would have been the largest of the LCP candidates, and the effect could be an increase or a decrease depending on whether it loads before or after the LCP candidate after the application of the exclusion. The change is applied to all Chrome versions 109 onward, but is largely coupled with Chrome 112 that was released a week ago.[131] This would be cited as a reason for the decrease in LCP pass rates in April 2023[18] and May 2023.[19]
2023 May 10 (announcement) for planned change March 2024 Release Metric status update Interactivity/responsiveness (First Input Delay (FID) and Interaction to Next Paint (INP)) Field data Google announces that Interaction to Next Paint (INP) will replace First Input Delay (FID) in the list of core web vitals, with the replacement planned for March 2024. As of the date of announcement, INP is immediately changed from an "experimental" metric to a "pending" core web vital.[132][133][134][135] On the same day, it is announced that the INP metric is available in the CrUX BigQuery, API, and History API both with and without the experimental prefix.[136]
2023 June 5 Insight All Field data Dan Shappir's talk comparing JavaScript frameworks in terms of their performance on real-world data is published, along with a transcript.[137]
2023 August 11 New version Browser behavior Loading speed (LCP), visual stability (CLS) Field data An experimental change is rolled out to 50% of Chrome users starting on this date, starting with around Chome 116, whereby the priority of the first five sufficiently large images is increased from low to medium from their default of low; images with an explicit 'fetchpriority' are not affected. The experiment also allows for two medium-priority resources at a time to be loading while Chrome's loading scheduler is in “tight mode” (up until the body has been inserted into the document). This is expected to improve both LCP and CLS, with a bigger effect on CLS (as the images are more likely to be downloaded prior to rendering).[23]
2023 August 22 New version Browser behavior Loading speed (LCP) Field data Over a 14-day rollout period starting on this day, Chrome changes the way animated images and videos are considered for LCP. For animated images, the change "counts the time that the first frame of the animation is displayed, if the image becomes an LCP candidate." (In contrast, the prior behavior was to wait for the animation to fully load). This change is expected to improve LCP. For videos, they were previously ignored as LCP candidates unless they had a poster image; now they are included as LCP candidates, with the first video frame being used to determine the time of loading. This change is expected to worsen LCP for pages where the video element would become the LCP element.[24]

See also

References

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  132. ↑ Viscomi, Rick; Sullivan, Annie (May 10, 2023). "Advancing Interaction to Next Paint. INP is no longer experimental. Learn about Chrome's plan to make it a Core Web Vital in 2024.". web.dev. Retrieved June 2, 2023. 
  133. ↑ "Introducing INP to Core Web Vitals". Google Search Central Blog. May 10, 2023. Retrieved June 2, 2023. 
  134. ↑ Montti, Roger (May 11, 2023). "New Core Web Vitals Metric Coming: Interaction To Next Paint. Interaction to Next Paint is elevated to Pending Core Web Vital Metric". Search Engine Journal. Retrieved February 25, 2024. 
  135. ↑ Woodhead, William (June 20, 2023). "INP. Get ready for the new Core Web Vital". Cloudflare blog. Retrieved February 25, 2024. 
  136. ↑ "The 202304 dataset is live". May 10, 2023. Retrieved June 2, 2023. 
  137. ↑ Shappir, Dan (June 5, 2023). "Comparing JavaScript Frameworks Performance Using Real-World Data". GitNation. Retrieved July 17, 2023. 
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