emshack@chromium.org chrome-desktop-ui-sea@google.com The type of Page Action currently shown. Logged once per ephemeral page action the first time it becomes visible on a given page. Tab switches will only trigger logging for any page actions that have not already been logged as visible on this page. Histogram is in the process of being removed in in favor of Extensions.ExtensionsWithPageActions that emits only on profile open for "user" profiles (profiles where people can install extensions, specifically profiles that can have non-component extensions installed). rdevlin.cronin@chromium.org extensions-core@chromium.org The number of Extensions that have Page Actions. Measured once per profile open. emshack@chromium.org chrome-desktop-ui-sea@google.com Records events related to overall ephemeral page action icon click through rate (CTR) calculation. The CTR can be calculated by computing "Clicked" / "Shown". "Clicked" means the page action icon was clicked. "Shown" means that the page action icon was displayed. "Shown" is logged once per page action the first time it becomes visible on a given page, and "Clicked" is logged once per click. emshack@chromium.org chrome-desktop-ui-sea@google.com The number of ephemeral Page Actions currently shown. Measured each time a page action icon is clicked. emshack@chromium.org chrome-desktop-ui-sea@google.com The number of ephemeral Page Actions currently shown. Measured each time a new page is loaded, and then again when each new page action appears on the same page. emshack@chromium.org chrome-desktop-ui-sea@google.com Records events related to percentage of pages with actions calculation. The percentage of pages with at least one ephemeral action shown can be calculated by computing "Action Shown" / "Page Shown". The percentage of pages with multiple ephemeral actions shown can be calculated by computing "Multiple Actions Shown" / "Page Shown". "Page Shown" is logged once when a given page is first loaded, "Action Shown" is logged when the first page action is displayed on a given page, and "Multiple Actions Shown" is logged the first time a page action appears on a given page alongside a second page action. emshack@chromium.org chrome-desktop-ui-sea@google.com Records events related to {PageActionType} page action icon click through rate (CTR) calculation. The CTR can be calculated by computing "Clicked" / "Shown". "Clicked" means the page action icon was clicked. "Shown" means that the page action icon was displayed. "Shown" is logged once per page action the first time it becomes visible on a given page, and "Clicked" is logged once per click. jkarlin@chromium.org johnidel@chromium.org chrome-analysis-team@google.com Records the time from frame navigation start to FirstContentfulPaint of each ad frame that receives a FirstContentfulPaint. The time could be quite large, as some ads don't paint until they're scrolled into view. But the metric is still useful in aggregate. Recorded for all ad frames with non-zero bytes or cpu usage that receive a FirstContentfulPaint. Recorded when the ad frame or page is destroyed. Changes to how cross-origin content is loaded (e.g., security policies, network prioritization) or to iframes can certainly affect this metric. Do not modify this metric in any way without contacting chrome-analysis-team@google.com. altimin@chromium.org bmcquade@chromium.org hajimehoshi@chromium.org Counts the events related to the back-forward cache, like when the page is put into the back-forward cache. jkarlin@chromium.org johnidel@chromium.org chrome-ads-histograms@google.com Only recorded if the page has at least one identified ad frame. Recorded in PageLoadMetrics when the page is destroyed. Bytes include all bytes used by the network to load a resource and response body bytes for cached resources (from both the HTTP and memory caches). An ad frame consists of the identified ad frame and all of its children (which may also be ads, but are counted as part of the ancestor ad frame). Includes resources that did not finish loading. Warning: This metric expired around 01/2023 and was unexpired 07/2023. Data may be missing. alexmt@chromium.org johnidel@chromium.org Total number of network bytes that went towards loading non-ad resources for a single page over its entire lifetime. This includes resources that did not finish or were canceled. Only recorded for pages with non-zero total bytes, including those without an ad frame and pages with no ad resources. Recorded when the page is destroyed. alexmt@chromium.org johnidel@chromium.org The percentage of network bytes loaded by the page that are attributed to ad resources (including ad resources in the main frame) across the entire page load. Only recorded for pages with non-zero network bytes, including those without an ad frame and pages with no ad resources. Recorded when the page is destroyed. alexmt@chromium.org johnidel@chromium.org The percentage of all bytes loaded by the page that are attributed to ad resources (including ad resources in the main frame) across the entire page load. Only recorded for pages with non-zero total bytes, including those without an ad frame and pages with no ad resources. Recorded when the page is destroyed. johnidel@chromium.org jkarlin@chromium.org Records whether the heavy ad intervention was disallowed by the blocklist on a frame. Only recorded when the heavy ad blocklist is enabled and available (e.g. this is not recorded in incognito mode). johnidel@chromium.org justinmiron@google.com Records the number of network bytes used by a heavy ad unloaded due to network usage by the heavy ad intervention. It is recorded at the time of unload and the value may be larger than the heavy ads threshold due to the delay in unloading an ad. cammie@chromium.org jkarlin@chromium.org johnidel@chromium.org chrome-ads-histograms@google.com The maximum reported number of kilobytes of memory used by V8 by the main frame in this pageload. Only recorded if the page has at least one identified ad frame. Recorded in PageLoadMetrics when the page is destroyed. An ad frame consists of the identified ad frame and all of its children (which may also be ads, but are counted as part of the ancestor ad frame). cammie@chromium.org jkarlin@chromium.org johnidel@chromium.org chrome-ads-histograms@google.com The number of V8 memory measurement updates received by AdsPageLoadMetricsObserver per pageload. Only recorded if the page has at least one identified ad frame. Recorded in PageLoadMetrics when the page is destroyed. johnidel@chromium.org jkarlin@chromium.org Total number of network bytes that went towards loading ad resources for a single page over it's entire lifetime. This includes resources that did not finish or were canceled. Only recorded for pages with non-zero ad bytes. bmcquade@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from the user input that triggers the top-level navigation for an AMP document to the time that the navigation for the AMP document is initiated in the AMP frame. This gives insight into how often AMP documents are navigated to via same document navigations without being prerendered. This histogram has incomplete data. It expired after M78 and was re-added in M90. bmcquade@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from the main frame navigation to the subsequent subframe navigation for the AMP document. Only recorded for non-same-page navigations. This histogram has incomplete data. It expired after M78 and was re-added in M90. bmcquade@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per navigation, in an AMP subframe document. Recorded on first page interaction. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. Only non-same-document navigations are included. This histogram has incomplete data. It expired after M78 and was re-added in M90. sullivan@chromium.org speed-metrics-dev@chromium.org The number of interactions of a page load, in AMP subframe. Definition of an interaction: https://web.dev/better-responsiveness-metric/#group-events-into-interactions iclelland@chromium.org speed-metrics-dev@chromium.org The {NormalizedResponsivenessMetric} of a page load, in AMP subframes, in ms. For this metric, we measure the latency of a user interaction by the {UserInteractionLatency} within the user interaction. Full navigation means we only include non-same-document navigations, otherwise we only include same-document navigations. Recorded at the end of the AMP document lifetime, such as when the document is being navigated away from. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in the AMP subframe. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. If {Bfcache} is triggered, we record the metric when the user navigates away or closes the page after the page was restored from back-forward cache. Otherwise, we record it at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. Recorded for non same-document AMP navigations in the main frame, at the end of the AMP document lifetime, such as when the document is being navigated away from. Replaces PageLoad.Clients.AMP.LayoutInstability.MaxCumulativeShiftScore.Subframe.SessionWindow.Gap1000ms.Max5000ms and increases granularity in order to get more coverage for ~40% of the values in the 0-0.1 range. iclelland@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a {Window}, in the AMP subframe. The gap between two consecutive shifts in a window is not bigger than {Gap} and the maximum window size is {MaxWindowSize}. This metric's integral value is 100x the fractional cumulative layout shift score described in the explainer. If the {Navigation} is FullNavigation, we record the metric for non same-document AMP navigations in the main frame, at the end of the AMP document lifetime, such as when the document is being navigated away from. Otherwise, only same-document navigations are included. bmcquade@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from user input to first "contentful" paint in an AMP subframe document. Will be zero or near-zero in cases where the AMP subframe document was prerendered. Only same-document navigations are included. This histogram has incomplete data. It expired after M78 and was re-added in M90. bmcquade@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from user input to first "contentful" paint in an AMP subframe document. Only non-same-document navigations are included. This histogram has incomplete data. It expired after M78 and was re-added in M90. bmcquade@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from user input to largest "contentful" paint in an AMP subframe document. Only same-document navigations are included. Excludes any content painted after user input. The value is recorded at the end of each page load unless there is an abort or user input before text or image paint. See http://bit.ly/fcp_plus_plus for details. Will be zero or near-zero in cases where the AMP subframe document was prerendered. This histogram has incomplete data. It expired after M78 and was re-added in M90. bmcquade@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from user input to largest "contentful" paint in an AMP subframe document. Only non-same-document navigations are included. Excludes any content painted after user input. The value is recorded at the end of each page load unless there is an abort or user input before text or image paint. See http://bit.ly/fcp_plus_plus for details. This histogram has incomplete data. It expired after M78 and was re-added in M90, and also after 2022-12-11 until M111. lbrady@google.com shivanisha@chromium.org dom@chromium.org Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per navigation. Recorded on first FencedFrames' page interaction. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. toyoshim@chromium.org mparch-dev@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred on the FencedFrames page (including all subframes). Higher values correspond to greater instability, which is bad. Recorded at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. On Android it's done when the browser is backgrounded. lbrady@google.com shivanisha@chromium.org dom@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred in the FencedFrames page's main frame. Recorded at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. On Android, it's done when the browser is backgrounded. toyoshim@chromium.org mparch-dev@chromium.org The time from navigation start to first "contentful" paint. This metric does not include all FencedFrames' page loads. Recorded iff the page loads and the event happens in the foreground. lbrady@google.com shivanisha@chromium.org dom@chromium.org Measures the time from navigation timing's navigation start to the time the first image is painted, for FencedFrames' main frame documents. For images that render progressively, this is recorded as soon as any image pixels have been drawn iff the page loads and the event happens in the foreground. toyoshim@chromium.org mparch-dev@chromium.org Measures the time from navigation timing's navigation start to the time the first paint is performed, for FencedFrames' main frame documents. Recorded iff the page loads and the event happens in the foreground. toyoshim@chromium.org mparch-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, across all frames under the FencedFrames root. Excludes any content painted after user input. Includes content that has been removed from the page. See web.dev/lcp for more details. The value is recorded at the end of each page load or the latest time when we can reliably record: when the page is navigated away, the browser is closed, or on Android when the browser is backgrounded, iff the page loads and the event happens in the foreground. tluk@chromium.org chrome-cros@chromium.org Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per navigation. See https://goo.gl/tr1oTZ for a detailed explanation. Only recorded for side search navigations from the side panel that happen entirely in the foreground. tluk@chromium.org chrome-cros@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a Window. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. Only recorded for side search navigations from the side panel. The metric is emitted when the navigation is completed or the app is backgrounded on Android. tluk@chromium.org chrome-cros@chromium.org Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints content, in the AMP subframe. A contentful paint includes a paint of text, image, SVG, or canvas. Only recorded for side search navigations from the side panel that happen entirely in the foreground. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the first image is painted, for main frame documents. For images that render progressively, this is recorded as soon as any image pixels have been drawn. Only recorded for side search navigations from the side panel that happen entirely in the foreground. tluk@chromium.org chrome-cros@chromium.org Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints the experimental largest content (text or image) within viewport, in the AMP subframe. See http://bit.ly/largest_contentful_paint_explainer for more details. Differs from SubFrame.PaintTiming.NavigationToLargestContentfulPaint in that removed content is still considered a valid candidate. Only recorded for side search navigations from the side panel that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. spelchat@chromium.org chrome-brapp-loading@google.com Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints content, for Google Search page loads. A contentful paint includes a paint of text, image, SVG, or canvas. Only recorded for Search navigations that start in the foreground and stay in the foreground until the first contentful paint. spelchat@chromium.org chrome-brapp-loading@google.com Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints the experimental largest content (text or image) within viewport, for Google Search page loads. See http://bit.ly/largest_contentful_paint_explainer for more details. Differs from SubFrame.PaintTiming.NavigationToLargestContentfulPaint in that removed content is still considered a valid candidate. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. spelchat@chromium.org chrome-brapp-loading@google.com Measures the time from navigation timing's navigation start to the time the parser started, for Google Search page loads. Only recorded for Search navigations that start in the foreground and stay in the foreground until parse start. kouhei@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Measures the time from navigation start to the first contentful paint. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data. kouhei@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Measures the time from navigation start to the largest contentful paint. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data. chikamune@chromium.org chrome-loading@google.com {Timing} {OtherLoadingCount} {Background} nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.InteractiveTiming.FirstInputDelay4, but for page loads that were prerendered and were later activated. Note that prerendered page loads are excluded from PageLoad.InteractiveTiming.FirstInputDelay4. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.LayoutInstability.CumulativeShiftScore.MainFrame, but for page loads that were prerendered and were later activated. Note that prerendered page loads are excluded from PageLoad.LayoutInstability.CumulativeShiftScore.MainFrame. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.LayoutInstability.CumulativeShiftScore, but for page loads that were prerendered and were later activated. Note that prerendered page loads are excluded from PageLoad.LayoutInstability.CumulativeShiftScore. kenoss@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.LayoutInstability.MaxCumulativeShiftScore.SessionWindow.Gap1000ms.Max5000ms2, but for page loads that were prerendered and were later activated. Note that prerendered page loads are excluded from PageLoad.LayoutInstability.MaxCumulativeShiftScore.SessionWindow.Gap1000ms.Max5000ms2. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS Measures the time from the start of initial prerendering navigation to the start of activation navigation. This corresponds to the activationStart attribute of PerformanceNavigationTiming. Recorded when a prerendered page is activated. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.PaintTiming.NavigationToFirstContentfulPaint, but for page loads that were prerendered and were later activated. This measures the time relative to the activation navigation start. Note that prerendered page loads are excluded from PageLoad.PaintTiming.NavigationToFirstContentfulPaint. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.PaintTiming.NavigationToFirstPaint, but for page loads that were prerendered and were later activated. This measures the time relative to the activation navigation start. Note that prerendered page loads are excluded from PageLoad.PaintTiming.NavigationToFirstPaint. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.PaintTiming.NavigationToLargestContentfulPaint2, but for page loads that were prerendered and were later activated. This measures the time relative to the activation navigation start. Note that prerendered page loads are excluded from PageLoad.PaintTiming.NavigationToLargestContentfulPaint2. linnan@chromium.org johnidel@chromium.org measurement-api-dev+metrics@google.com PageLoad.InteractiveTiming.FirstInputDelay4, but recorded iff {PrivacySandboxAdsApi} was used in the page. linnan@chromium.org johnidel@chromium.org measurement-api-dev+metrics@google.com PageLoad.LayoutInstability.MaxCumulativeShiftScore.SessionWindow.Gap1000ms.Max5000ms2, but recorded iff {PrivacySandboxAdsApi} was used in the page. linnan@chromium.org johnidel@chromium.org measurement-api-dev+metrics@google.com PageLoad.PaintTiming.NavigationToFirstContentfulPaint, but recorded iff {PrivacySandboxAdsApi} was used in the page. linnan@chromium.org johnidel@chromium.org measurement-api-dev+metrics@google.com PageLoad.PaintTiming.NavigationToLargestContentfulPaint2, but recorded iff {PrivacySandboxAdsApi} was used in the page. sisidovski@chromium.org chrome-worker@google.com The {Timing} time of pages with the Service Worker fetch handlers. Metrics won't be recorded if pages are not controlled by service workers. This is recorded only when the ServiceWorker script is eligible for the experiment. yyanagisawa@chromium.org chrome-worker@google.com The {Timing} time of pages with the Service Worker fetch handlers. Metrics won't be recorded if pages are not controlled by service workers. The metrics are broken down by {HandlerType}. {HandlerType} only explains the page's handler type, and it does not mean the fetch handler is actually skipped or not. tluk@chromium.org chrome-cros@chromium.org Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per navigation. See https://goo.gl/tr1oTZ for a detailed explanation. Only recorded for side search navigations from the side panel. tluk@chromium.org chrome-cros@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a Window. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. Only recorded for side search navigations from the side panel. This is recorded when the side search WebContents in the side panel is navigated. tluk@chromium.org chrome-cros@chromium.org Measures the time from navigation start to first contentful paint. Only recorded for side search navigations from the side panel. tluk@chromium.org chrome-cros@chromium.org Measures the time from navigation start to largest contentful paint. Only recorded for side search navigations from the side panel. This is recorded when the side search WebContents in the side panel is navigated. jkarlin@chromium.org johnidel@chromium.org The time from navigation start to the first contentful paint of third-party (in respect to scheme://eTLD+1) frames on pages. Note that this can be significantly delayed due to lazy loading. Note also that all of the PageLoad.Clients.ThirdParty.Frames metrics will only be recorded for the first kMaxRecordedFrames (50) active iframe RenderFrameHosts (at any given time). awillia@chromium.org djmitche@chromium.org The time from navigation start to the first contentful paint of third-party opaque origin frames on pages. Note that this metric is only collected when the top-level origin is not opaque. Also, this metric can be significantly delayed due to lazy loading. Note also that all of the PageLoad.Clients.ThirdParty.Frames metrics will only be recorded for the first kMaxRecordedFrames (50) active iframe RenderFrameHosts (at any given time). awillia@chromium.org djmitche@chromium.org The time from navigation start to the largest contentful paint of third-party opaque origin frames on pages. Note that this metric is only collected when the top-level origin is not opaque. Note also that all of the PageLoad.Clients.ThirdParty.Frames metrics will only be recorded for the first kMaxRecordedFrames (50) active iframe RenderFrameHosts (at any given time). jkarlin@chromium.org yaoxia@chromium.org The number of third party (in respect to scheme://eTLD+1) origins on a page that read cookies either via resource request headers or document.cookie. This metric was expired between May and August 2023 and may be missing data. shivanisha@chromium.org jkarlin@chromium.org Records the largest contentful paint only for pages that load a third party font and whose largest contentful resource type is text. See PageLoad.PaintTiming.NavigationToLargestContentfulPaint2 for details. kenoss@chromium.org toyoshim@chromium.org The duration of UseCounterPageLoadMetricsObserver::DidActivatePrerenderedPage. Recorded iff the page is prerendered and activated. When a page is prerendered, metrics "Blink.UseCounter.*" are buffered into memory. When a page is activated then, buffered metrics are flushed and recorded. This metric records the duration of this flush, in case of this cause a performance degradation. Warning: this histogram was expired from 2023-03-16 to 2023-03-29; data may be missing. nidhijaju@chromium.org blink-network-stack@google.com Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints content, for page loads that can use zstd. A contentful paint includes a paint of text, image, SVG, or canvas. Only recorded for navigations that start in the foreground and stay in the foreground until the first contentful paint. nidhijaju@chromium.org blink-network-stack@google.com Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints the experimental largest content (text or image) within viewport, for page loads that can use zstd. See https://github.com/w3c/largest-contentful-paint for more details. Differs from SubFrame.PaintTiming.NavigationToLargestContentfulPaint in that removed content is still considered a valid candidate. Only recorded for navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. nidhijaju@chromium.org blink-network-stack@google.com Measures the time from navigation timing's navigation start to the time the parser started, for page loads that can use zstd. Only recorded for navigations that start in the foreground and stay in the foreground until parse start. This metric is emitted when the parser starts for a navigation. chikamune@chromium.org loading-dev@chromium.org PageLoad.PaintTiming.NavigationToFirstContentfulPaint, but recorded only for {Origin} navigations. chikamune@chromium.org loading-dev@chromium.org PageLoad.InteractiveTiming.FirstInputDelay4, but recorded only for {Origin} navigations. chikamune@chromium.org loading-dev@chromium.org PageLoad.PaintTiming.NavigationToLargestContentfulPaint2, but recorded only for {Origin} navigations. chikamune@chromium.org loading-dev@chromium.org PageLoad.LayoutInstability.CumulativeShiftScore, but recorded only for {Origin} navigations. chikamune@chromium.org loading-dev@chromium.org PageLoad.LayoutInstability.CumulativeShiftScore.MainFrame, but recorded only for {Origin} navigations. johnidel@chromium.org chrome-ads-histograms@google.com Only recorded if the page has at least one identified ad frame. Recorded in PageLoadMetrics when the page is destroyed. Cpu measures the wall time of tasks attributable to a frame as reported by the MainThreadTaskScheduler as well as time spent servicing scripted animations by each document (not attributable by the MainThreadTaskScheduler). An ad frame consists of the identified ad frame and all of its children (which may also be ads, but are counted as part of the ancestor ad frame). Includes resources that did not finish loading. Does not consider time while a page is backgrounded. Warning: This metric expired around 04/2022 and was unexpired 07/2023. Data may be missing. alexmt@chromium.org johnidel@chromium.org Recorded when the page is destroyed or the app is backgrounded on mobile. Records the total wall time of tasks attributable to the page across its lifetime. Considers both the CPU usage while the page is in the foreground and in the background. alexmt@chromium.org johnidel@chromium.org Recorded when the page is destroyed or the app is backgrounded on mobile. Records the total wall time of tasks attributable to the page across its lifetime. Does not consider CPU usage while a page is backgrounded. bmcquade@chromium.org csharrison@chromium.org Measures the time from navigation timing's navigation start to the time the DOMContentLoaded event is fired, for main frame documents. bmcquade@chromium.org csharrison@chromium.org Measures the time from navigation timing's navigation start to the time the load event is fired, for main frame documents. This experimental metric has been removed from the code. bmcquade@chromium.org csharrison@chromium.org This metric is still experimental and not yet ready to be relied upon. Measures the time from navigation start to the time the page load was aborted due to being backgrounded. This experimental metric has been removed from the code. csharrison@chromium.org This metric is still experimental and not yet ready to be relied upon. Measures the time from navigation start to the time the page load was aborted by the user closing the tab or browser. This experimental metric has been removed from the code. csharrison@chromium.org This metric is still experimental and not yet ready to be relied upon. Measures the time from navigation start to the time the page load was aborted by a forward or back navigation. This experimental metric has been removed from the code. csharrison@chromium.org This metric is still experimental and not yet ready to be relied upon. Measures the time from navigation start to the time the page load was aborted by a new navigation. This experimental metric has been removed from the code. csharrison@chromium.org This metric is still experimental and not yet ready to be relied upon. Measures the time from navigation start to the time the page load was aborted. The abort cause is unknown. This experimental metric has been removed from the code. csharrison@chromium.org This metric is still experimental and not yet ready to be relied upon. Measures the time from navigation start to the time the page load was aborted by a reload. This experimental metric has been removed from the code. csharrison@chromium.org This metric is still experimental and not yet ready to be relied upon. Measures the time from navigation start to the time the page load was aborted by the user pressing stop. dougarnett@chromium.org tbansal@chromium.org sullivan@chromium.org The maximum size click input burst for the page load. A click input burst is a sequence of user click inputs at approximately the same screen position where the clicks each occur soon after the previous one (e.g., within half second). This is intended to detect possible rage clicks by the user. Note: stat collection stopped in August 2021, and resumes in February 2023. spelchat@chromium.org chrome-brapp-loading@google.com The time between the OS-level input event that initiated a navigation, and the navigation actually starting. spelchat@chromium.org chrome-brapp-loading@google.com The time between the OS-level input event that initiated a navigation, and the navigation actually starting, for background loads. spelchat@chromium.org chrome-brapp-loading@google.com The time between the OS-level click/tap event and navigation start, for clicks on links in the renderer. spelchat@chromium.org chrome-brapp-loading@google.com The time between the OS-level keypress/tap event in the omnibox and navigation start, for navigations from the omnibox. This experimental metric has been replaced by PageLoad.LayoutInstability.CumulativeShiftScoreAtFirstOnHidden in M113, which is now an official histogram without any change in the implementation. lanwei@chromium.org speed-metrics-dev@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred on the page (including all subframes) until the first time the page moves from the foreground to the background. It is recorded when the tab is first hidden after it is first shown in foreground. This metric is trying to record the layout shift values which are not able to be recorded in PageLoad.LayoutInstability.CumulativeShiftScore for some reasons. This experimental metric has been removed from the code and it is replaced by PageLoad.LayoutInstability.MaxCumulativeShiftScoreAtFirstOnHidden.SessionWindow.Gap1000ms.Max5000ms which increases granularity to get coverage for ~25% of the values in the 0-0.1 range by using 50 buckets for the 0.0-2.4 range instead of 0.0-10.0 range in M113. lanwei@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a Window until the first time the page moves from the foreground to the background. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. It is recorded when the tab is first hidden after it is first shown in foreground. This metric is trying to record the layout shift values which are not able to be recorded in PageLoad.LayoutInstability.MaxCumulativeShiftScore.SessionWindow.Gap1000ms.Max5000ms2 for some reasons. cammie@chromium.org jkarlin@chromium.org johnidel@chromium.org The maximum reported number of kilobytes of memory used by V8 by the main frame in this pageload. Only recorded if memory tracking is enabled. Recorded in PageLoadMetrics when the page is destroyed. cammie@chromium.org jkarlin@chromium.org johnidel@chromium.org The maximum reported aggregate number of kilobytes of memory used by V8 by subframes in this pageload. The value recorded is the maximum simultaneous usage by all subframes during this pageload, not including the main frame. Only recorded if memory tracking is enabled. Recorded in PageLoadMetrics when the page is destroyed. cammie@chromium.org jkarlin@chromium.org johnidel@chromium.org The maximum reported aggregate number of kilobytes of memory used by V8 by all frames in this pageload. The value recorded is the maximum simultaneous usage by all frames during this pageload, including the main frame. Only recorded if memory tracking is enabled. Recorded in PageLoadMetrics when the page is destroyed. nhiroki@chromium.org chrome-loading@google.com The interval between when a callback for the navigation loader is last invoked and when navigation commit message is sent to a renderer process for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The interval between when the final HTTP request is sent and when the headers of the final HTTP response is received for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The interval between when the headers of the final HTTP response is received and when a callback for the navigation loader is last invoked for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The interval between when the first HTTP request is sent and when the headers of the first HTTP response is received for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The interval between when the headers of the first HTTP response is received and when a callback for the navigation loader is first invoked for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that a callback for the navigation loader is last invoked for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that the final HTTP request is sent for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that the headers of the final HTTP response is received for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that a callback for the navigation loader is first invoked for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that the first HTTP request is sent for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that the headers of the first HTTP response is received for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that navigation commit message for a main frame navigation is sent to a renderer process. cduvall@chromium.org jam@chromium.org Measures the time from load start to when headers have been received for resource requests which come from the cache. Logged for every {RequestDestination} resource request from the cache. cduvall@chromium.org jam@chromium.org Measures the time from when the navigation commit was sent to the renderer to the first subresource load start. Logged for every page load which has subresources. cduvall@chromium.org jam@chromium.org Measures the time from navigation start to the first subresource load start. Logged for every page load which has subresources. cduvall@chromium.org jam@chromium.org Measures the time from load start to when headers have been received for resource requests which do not come from the cache. Logged for every {RequestDestination} resource request which is not from the cache. cduvall@chromium.org jam@chromium.org Measures the aggregate time of subresource requests (from start to when headers have been received) which have been completed before the first contentful paint. Logged for every page load. iclelland@chromium.org speed-metrics-dev@chromium.org Determines the final status for this page load. That is, records whether the page was never foregrounded, was foregrounded but did not reach FCP, or did reach FCP. The metric is recorded at the end of each page load. As usual with PageLoad metrics, we consider app backgrounding on Android to be the end of page load as well as the app could be evicted by Android anytime after that happens. toyoshim@chromium.org chrome-prerendering@google.com The page visit type that represents if the page follows a link navigation, and the page is followed by another link navigation. This metrics is recorded when the page is destructed. cduvall@chromium.org jam@chromium.org Measures the time from when the page is first eligible to paint to when the first paint occurs. Logged for every foreground page load. sullivan@chromium.org The time between the OS-level input event that initiated a navigation, and the first contentful paint of the page that was loaded in the navigation. npm@chromium.org toyoshim@chromium.org speed-metrics-dev@chromium.org chrome-prerendering@google.com The total amount of time the page spent in the foreground on {PageVisitType}. Note that this metric adds all foreground durations occurring for the page. For example: if the page starts foregrounded during 1 second, then goes to the background for a while, then is foregrounded again for 2 seconds, and then is unloaded, this metric reports 3 seconds. The metric is recorded at the end of each page load. As usual with PageLoad metrics, we consider app backgrounding on Android to be the end of page load as well as the app could be evicted by Android anytime after that happens. See also PageLoad.Experimental.PageVisitType for each page visit type definition. cammie@chromium.org jkarlin@chromium.org chrome-ads-histograms@google.com For each identified ad frame, whether the origin of the ad creative frame matches or differs from the origin of the main frame. The ad creative frame is heuristically determined, from among an identified ad frame and all of its children, as the first of these frames to record a First Contentful Paint. If no FCP is recorded, the creative origin status is marked as indeterminate. cammie@chromium.org jkarlin@chromium.org chrome-ads-histograms@google.com For each identified ad frame, whether the origin of the ad creative frame matches or differs from the origin of the main frame, further split by whether the frame has lifecycle updates throttled. Metric is emitted on frame deletion. The ad creative frame is heuristically determined, from among an identified ad frame and all of its children, as the first of these frames to record a First Contentful Paint. If no FCP is recorded, the creative origin status is marked as indeterminate. Frames that are render-throttled will not have an FCP. Ad frames with indeterminate creative origin status are broken out as throttled or not. johnidel@chromium.org chrome-ads-histograms@google.com For each identified ad frame, whether the origin of the ad matches the origin of the main frame, differs from the origin of the main frame, or is indeterminable. An ad frame consists of the identified ad frame and all of its children (which may also be ads, but are counted as part of the ancestor ad frame). Frames of zero bytes (e.g., never had a document or their document was doc.written and no sub-resources were loaded) are not counted. Warning: This metric expired around 04/2022 and unexpired 07/2023. Data may be missing. johnidel@chromium.org csharrison@chromium.org For each identified ad frame, whether the sticky user activation bit was ever set on the frame. Recorded for each ad frame when the page is destroyed or navigated away from, including ad frames that no longer exist. An ad frame consists of the identified ad frame and all of its children (which may also be ads, but are counted as part of the ancestor ad frame). Frames of zero bytes (e.g., never had a document or their document was doc.written and no sub-resources were loaded) are not counted. jkarlin@chromium.org johnidel@chromium.org The number of frames on the page that have loaded more than 0 bytes of content or had non-zero CPU usage. For pages with zero ad frames, the other PageLoad.Clients.Ads metrics are not recorded unless otherwise specified. This metric is not recorded on sites where the subresource filter is enabled. Child frames of an ad frame are not included in the count. johnidel@chromium.org jkarlin@chromium.org Records heavy ad type for each ad frame, as determined by the first threshold hit (see FrameData::HeavyadStatus). This is recorded regardless of feature flag or other conditions that prevent the heavy ad intervention from occuring. This includes 1 megabyte of random additive noise on the network threshold. As such, it is possible for this histogram to record different values for the same frame than PageLoad.HeavyAds.ComputedType2. Recored for all ad frames with non-zero bytes. Recorded when the ad frame destroyed or when the page is destroyed. It is possible for multiple thresholds to be hit at the same time, with the higher valued enums winning those race conditions. johnidel@chromium.org jkarlin@chromium.org Records the type of heavy ad unloaded by the heavy ad intervention. Heavy ad type is determined by the first threshold hit. This is not recorded for ad frames that are considered heavy but did not fufill other criteria for the intervention. This includes the feature being enabled and being below the per-origin intervention cap. It is possible for multiple thresholds to be hit at the same time, with the higher valued enums winning those race conditions. altimin@chromium.org hajimehoshi@chromium.org bfcache-dev@chromium.org speed-metrics-dev@chromium.org Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per back-forward navigation. Recorded on first page interaction after the page is restored from the back-forward cache. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.InteractiveTiming.FirstInputDelay4. These two histograms will be aggregated on the server to form the authoritative metric. altimin@chromium.org hajimehoshi@chromium.org bfcache-dev@chromium.org speed-metrics-dev@chromium.org iOS only. This is the same as PageLoad.InteractiveTiming.FirstInputDelay.AfterBackForwardCacheRestore, but uses the same bucketing on iOS as non-iOS platforms use in that metric. Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per back-forward navigation. Recorded on first page interaction after the page is restored from the back-forward cache. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.InteractiveTiming.FirstInputDelay4_iOSFixed. These two histograms will be aggregated on the server to form the authoritative metric. sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per navigation. Recorded on first page interaction. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.InteractiveTiming.FirstInputDelay.AfterBackForwardCacheRestore. These two histograms will be aggregated on the server to form the authoritative metric. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com iOS only. This is the same as PageLoad.InteractiveTiming.FirstInputDelay4, but uses the same bucketing on iOS as non-iOS platforms use in that metric. Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per navigation. Recorded on first page interaction. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.InteractiveTiming.FirstInputDelay.AfterBackForwardCacheRestore_iOSFixed. These two histograms will be aggregated on the server to form the authoritative metric. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog sullivan@chromium.org speed-metrics-dev@chromium.org The duration between navigation start and the hardware timestamp of the first meaningful input per navigation. Recorded on first page interaction. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com The duration between the hardware timestamp and the start of event processing on the main thread for a meaningful input. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. WARNING: The long tail of this metric is buggy on Mac (overflows for a subset of users) which can lead to surprising false regressions or improvements. sullivan@chromium.org speed-metrics-dev@chromium.org The duration between navigation start and the hardware timestamp of a meaningful input. Excludes scrolls. sullivan@chromium.org speed-metrics-dev@chromium.org The number of user interactions in a page load. Definition of interaction: https://web.dev/better-responsiveness-metric/#group-events-into-interactions iclelland@chromium.org speed-metrics-dev@chromium.org The duration between the start of event processing and the end of event processing on the main thread for a meaningful input. Excludes scrolls. This metric is recorded when users interact with the page, which may trigger input events such as pointerdown, keydown, click and mousedown. iclelland@chromium.org speed-metrics-dev@chromium.org The duration between the end of event processing and the time when the first paint was performed on the main thread for a meaningful input. Excludes scrolls. This metric is recorded when users interact with the page, which may trigger input events such as pointerdown, keydown, click and mousedown. iclelland@chromium.org speed-metrics-dev@chromium.org The {NormalizedResponsivenessMetric} of a page load {PageLoadType}, in ms. For this metric, we measure the latency of a user interaction by the {UserInteractionLatency} within the user interaction. Recorded at the end of the page load lifetime, such as when users navigate to a new web page, except UserInteractionLatencyAtFirstOnHidden.HighPercentile2, which is recorded when a page is moved from the foreground to the background for the first time. UserInteractionLatencyAtFirstOnHidden.HighPercentile2 is trying to record the INP values which are not able to be recorded in UserInteractionLatency.HighPercentile2 for some reasons. csharrison@chromium.org bmcquade@chromium.org Counts of various internal error conditions in the page_load_metrics system. zuoaoyuan@chromium.org speed-metrics-dev@chromium.org Records the number of unique presentation times that Event Timing has queued up, waiting to assign to Event Timing entries and dispatch to performance timeline. Recorded once every time a presentation promise resolves. The queue grows whenever a new presentation promise gets queued, and shrinks when it gets reported. Note that when a newer presentation promise gets resolved before an older one, we would delay reporting it so timings are reported in order. This should only happen whenever a newer presentation promise is not actually measuring to Next Paint. toyoshim@chromium.org src/components/page_load_metrics/OWNERS src/content/browser/preloading/prerender/OWNERS The status of validity check of PageLoadTiming structs received from the render process over IPC. Recorded when timing information is {Condition}. Warning: this histogram was expired from 2021-01-31 to 2023-01-13; data may be missing. toyoshim@chromium.org mparch-dev@chromium.org This records the Page type that each PageLoadTracker tracks. This metric is recorded when a PageLoadTracker is created for a Page. iclelland@chromium.org speed-metrics-dev@chromium.org Measures whether the largest contentful paint, whose timestamp is measured by PageLoad.PaintTiming.NavigationToLargestContentfulPaint2, comes from text or image. This value is recorded whenever PageLoad.PaintTiming.NavigationToLargestContentfulPaint2 is recorded. iclelland@chromium.org speed-metrics-dev@chromium.org Measures whether the largest contentful paint in the main frame, whose timestamp is measured by PageLoad.PaintTiming.NavigationToLargestContentfulPaint2.MainFrame, comes from text or image. This value is recorded whenever PageLoad.PaintTiming.NavigationToLargestContentfulPaint2.MainFrame is recorded. sullivan@chromium.org Breakdown of NavigationToFirstContentfulPaint counts by process that initiated the navigation (this will only be renderer or browser). lingqi@chromium.org chrome-prerendering@google.com Records error codes for loading of a main resource of a main frame which belongs to a prerendered and then activated page when the page received loading completion event for the resource. This metric is used to monitor whether preload cache intercepting logic causes extra page loading errors. kenoss@chromium.org src/content/browser/preloading/prerender/OWNERS Counts page load events related to Prerender2, like navigation in prerendered main frame and prerendering activation navigation. Recorded when those events are observed in PageLoadTracker. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS Records results of the foreground check per event type in PrerenderPageLoadMetricsObserver. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS Counts page load observer events related to Prerender2, like FirstContentfulPaint. Recorded when those events are observed in PrerenderPageLoaderMetricsObserver. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS Records the visibility of an initiator page in PageLoadTracker when a prerendered page gets activated. jonross@chromium.org graphics-dev@chromium.org This boolean keeps track of whether a valid presentation-timestamp was received or not. This is reported only for compositor-frames that report a paint-timing metric (e.g. FirstContentfulPaint etc.), and after that frame has been displayed on screen. The metric had expired on 2020-09-27, and re-enabled on 2021-03-17. So the data within this period is incomplete. mustaq@chromium.org blink-interactions-team@google.com Measures the number of events observed before the first paint. This metric is emitted for every committed page load, immediately after the first paint is complete. When the DropInputEventsBeforeFirstPaint feature is enabled, these events will be dropped as the user may not have seen the content they are interacting with yet. Since there is a delay from the first paint presentation to when the notification about it is received, the user may have actually seen the first paint for some of these events. If many events are being dropped, we may need to revisit this experiment or improve the measurement to only those after the first paint. mustaq@chromium.org blink-interactions-team@google.com Measures time difference between first paint and last event dropped by DropInputEventsBeforeFirstPaint feature. This metric is emitted for every committed page load, immediately after the first paint is complete. When the DropInputEventsBeforeFirstPaint feature is enabled, these events will be dropped as the user may not have seen the content they are interacting with yet. Since there is a delay from the first paint presentation to when the notification about it is received, the user may have actually seen the first paint for some of these events. If this time difference is long enough to affect user experience, we may need to revisit this experiment. We are logging 0 timestamp if there is no suppressed event or the most recent suppressed event is before the first paint time so that we have a count of the number of times the behavior was good to compare the size of the bad cases to. mustaq@chromium.org blink-interactions-team@google.com Measures the number of user-interactions observed before the first paint. The following low-level events are counted for this purpose because they mark the start of a user-interaction: MouseDown, RawKeyDown, KeyDown, TouchStart and PointerDown. This metric is emitted for every committed page load, immediately after the first paint is complete. When the DropInputEventsBeforeFirstPaint feature is enabled, these interactions will be dropped as the user may not have seen the content they are interacting with yet. Since there is a delay from the first paint presentation to when the notification about it is received, the user may have actually seen the first paint for some of these interactions. If it turns out that many interactions would be dropped, we will need to revisit our plan. bmcquade@chromium.org skobes@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred on the page (including all subframes). Higher values correspond to greater instability, which is bad. Recorded at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. Stable since M79; previous versions are expermental and subject to fluctuation between releases. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.LayoutInstability.CumulativeShiftScore.AfterBackForwardCacheRestore. These two histograms will be aggregated on the server to form the authoritative metric. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog altimin@chromium.org hajimehoshi@chromium.org bfcache-dev@chromium.org Measures the cumulative layout shift score (bit.ly/3fQz29y) that has occurred on the page (including all subframes) after the page is restored from the back-forward cache. Recorded when the user navigates away or closes the page after the page was restored from back-forward cache. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.LayoutInstability.CumulativeShiftScore. These two histograms will be aggregated on the server to form the authoritative metric. bmcquade@chromium.org skobes@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred in the main frame. Recorded at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. altimin@chromium.org hajimehoshi@chromium.org bfcache-dev@chromium.org Measures the cumulative layout shift score (bit.ly/3fQz29y) that has occurred in the main frame after the page is restored from the back-forward cache. Recorded when the user navigates away or closes the page after the page was restored from back-forward cache. lanwei@chromium.org speed-metrics-dev@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred on the page (including all subframes) until the first time the page moves from the foreground to the background. It is recorded when the tab is first hidden after it is first shown in foreground. This metric is trying to record the layout shift values which are not able to be recorded in PageLoad.LayoutInstability.CumulativeShiftScore for some reasons. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in after back forward cache restore. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. If {Bfcache} is triggered, we record the metric when the user navigates away or closes the page after the page was restored from back-forward cache. Otherwise, we record it at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. Replaces PageLoad.LayoutInstability.MaxCumulativeShiftScore.AfterBackForwardCacheRestore.SessionWindow.Gap1000ms.Max5000ms and increases granularity in order to get more coverage for ~5% of values in the 0-0.1 range. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a Window. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. If {Bfcache} is triggered, we record the metric when the user navigates away or closes the page after the page was restored from back-forward cache. Otherwise, we record it at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. Replaces PageLoad.LayoutInstability.MaxCumulativeShiftScore.SessionWindow.Gap1000ms.Max5000ms and increases granularity to get coverage for ~25% of the values in the 0-0.1 range. iclelland@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a {Window}. The gap between two consecutive shifts in a window is not bigger than {Gap} and the maximum window size is {MaxWindowSize}. This metric's integral value is 10x the fractional cumulative layout shift score described in the explainer. If {Bfcache} is triggered, we record the metric when the user navigates away or closes the page after the page was restored from back-forward cache. Otherwise, we record it at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. lanwei@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a Window until the first time the page moves from the foreground to the background. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. It is recorded when the tab is first hidden after it is first shown in foreground. This metric is trying to record the layout shift values which are not able to be recorded in PageLoad.LayoutInstability.MaxCumulativeShiftScore.SessionWindow.Gap1000ms.Max5000ms2 for some reasons. Replaced Experimental.LayoutInstability.MaxCumulativeShiftScoreAtFirstOnHidden.SessionWindow.Gap1000ms.Max5000ms and increases granularity to get coverage for ~25% of the values in the 0-0.1 range. bmcquade@chromium.org For page loads that start in the foreground, measures the duration of time until one of the following events occurs: the load of the main resource fails, the page load is stopped, the tab hosting the page is closed, the render process hosting the page goes away, a new navigation which later commits is initiated in the same tab, or the tab hosting the page is backgrounded. This metric has a very long tail, for pages that spend a long period of time in the foreground. As such, use of the mean or tail values are not recommended. jkarlin@chromium.org The time since navigation start before the user presses the back button on a page. Only measures page loads that remained in foreground and were created by user gesture inside the renderer (as opposed to browser UX gestures). bmcquade@chromium.org csharrison@chromium.org Measures the time from navigation timing's navigation start to the time the user first foregrounds an initially backgrounded tab. Only measures navigations that started in the background. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from a background tab being switched to the foreground to the time the first contentful paint is performed, for main frame documents. sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com The time from navigation start to first "contentful" paint. This metric does not include all page loads. If you need all page loads, add PageLoad.PaintTiming.NavigationToFirstContentfulPaint.Background. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.PaintTiming.NavigationToFirstPaint.AfterBackForwardCacheRestore. These two histograms will be aggregated on the server to form the authoritative metric. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the first image is painted, for main frame documents. For images that render progressively, this is recorded as soon as any image pixels have been drawn. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the first paint is performed, for main frame documents. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org. altimin@chromium.org djw@chromium.org bfcache-dev@chromium.org speed-metrics-dev@chromium.org Measures the time from back-forward navigation timing's navigation start to the time the first paint is performed, for main frame documents. Recorded only when the page is restored from back-forward cache. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.PaintTiming.NavigationToFirstContentfulPaint. altimin@chromium.org bfcache-dev@chromium.org speed-metrics-dev@chromium.org Meastures the time duration between the page restore from BFcache and the {Count} requestAnimationFrame time. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.PaintTiming.NavigationToFirstContentfulPaint. These two histograms will be aggregated on the server to form the authoritative metric. haoliuk@chromium.org speed-metrics-dev@chromium.org Records the count of cases where an LCP image candidate has an LCP less than its LoadEnd. This is counted once per LCP candidate in the PageLoadTracker::OnTimingChanged() method when the LCP candiate changes. haoliuk@chromium.org speed-metrics-dev@chromium.org Records the count of cases where an LCP image candidate has a LoadEnd less than its LoadStart. This is counted once per LCP candidate in the PageLoadTracker::OnTimingChanged() method when the LCP candiate changes. haoliuk@chromium.org speed-metrics-dev@chromium.org Records the count of cases where an LCP image candidate has a LoadStart less than the document TTFB. This is counted once per LCP candidate in the PageLoadTracker::OnTimingChanged() method when the LCP candiate changes. haoliuk@chromium.org speed-metrics-dev@chromium.org Records the count of 'causes' of LCP image load timings being less than document Time-To-First-Byte(TTFB) to diagnose crbug.com/1431906. This is recorded at most once per image, only when the image's load start was recorded as being before its associated document's TTFB. Recorded in the page load tracker when the LCP candidate changes. Unexplained instances are recorded in the 'Unknown' bucket, and these are expected to diminish over time as additional causes are uncovered. npm@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, across all frames. Excludes any content painted after user input. Includes content that has been removed from the page. See web.dev/lcp for more details. The value is recorded at the end of each page load or the latest time when we can reliably record: when the page is navigated away, the browser is closed, or on Android when the browser is backgrounded. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog sisidovski@google.com kouhei@chromium.org Similar to PaintTiming.NavigationToLargestContentfulPaint2, this measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints the largest content (text or image) in the cross-site subframe which is the top candidate of largest contentful paint. npm@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, for main frame documents. See PageLoad.PaintTiming.NavigationToLargestContentfulPaint2 for more information. lanwei@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, across all frames. Recorded at the point when a page which has been opened in the foreground is moved to the background for the first time. Excludes any content painted after user input. Includes content that has been removed from the page. See web.dev/lcp for more details. This metric is trying to record the LCP values which are not able to be recorded in PageLoad.PaintTiming.NavigationToLargestContentfulPaint2 for some reasons. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog bmcquade@chromium.org csharrison@chromium.org speed-metrics-dev@chromium.org Measures the time from when the HTML parser started, to when the page first paints content. bmcquade@chromium.org csharrison@chromium.org Measures the time from navigation timing's navigation start to the time the parser started, for main frame documents. cduvall@chromium.org swarm-team@google.com Measures the time that the HTML parser spent blocked on the execution of scripts, for main frame documents that finished parsing. This histogram has incomplete data. It expired on 2022-02-01 and was re-added on 2022-05-23. cduvall@chromium.org swarm-team@google.com Measures the time that the HTML parser spent blocked on the execution of scripts inserted from document.write, for main frame documents that finished parsing. This histogram has incomplete data. It expired on 2022-02-01 and was re-added on 2022-05-23. bmcquade@chromium.org csharrison@chromium.org Measures the time that the HTML parser spent blocked on the load of scripts, for main frame documents that finished parsing. sclittle@chromium.org offline-dev@chromium.org Reports the result of an attempt to load an MHTML archive.