Page-level Metrics

These are the metrics and measurements captured at a page-level and exposed in the JSON data.

Technical Page Metrics

• TTFB - Time to First Byte from when the navigation started until the first byte of page content is returned (after redirects)
• loadTime - (also fullyLoaded) Time to fully load the page
• docTime - Time until the document is complete (onLoad event)
• bytesIn - Number of bytes received
• bytesInDoc - Number of bytes received before the document complete time (onLoad event)
• bytesOut - Number of bytes transmitted
• bytesOutDoc - Number of bytes transmitted before the document complete time (onLoad event)
• loadEventStart - (also chromeUserTiming.loadEventStart) Start time of the last main-frame load event (before the event handlers run)
• loadEventEnd - (also chromeUserTiming.loadEventEnd) End time of the last main-frame load event (after the event has been handled)
• domContentLoadedEventStart - (also chromeUserTiming.domContentLoadedEventStart) Start time of the last main-frame domContentLoaded event (before the event handlers run)
• domContentLoadedEventEnd - (also chromeUserTiming.domContentLoadedEventEnd) End time of the last main-frame domContentLoaded event (after the event has been handled)
• chromeUserTiming.navigationStart - Chrome-reported time of the navigation start (RAIL)
• chromeUserTiming.fetchStart - Chrome-reported time of the fetch start (RAIL)
• chromeUserTiming.responseEnd - Chrome-reported time of the end of the initial response (RAIL)
• domLoading - (also chromeUserTiming.domLoading) - Browser-reported time of the time when the DOM state changed to loading (RAIL)
• domInteractive - (also chromeUserTiming.domInteractive) Browser-reported time of the time when the DOM state changed to interactive - not to be confused with TimeToInteractive (RAIL)
• domComplete - (also chromeUserTiming.domComplete) Browser-reported time of the time when the DOM state changed to complete (RAIL)
• basePageSSLTime - Time spent negotiating TLS for the base page
• connections - Number of connections used to load the page content
• requests - (also requestsFull) Number of individual requests to load the page
• requestsDoc - Number of requests before the document complete time (onLoad event)
• responses_200 - Number of requests that resulted in a 200 response code
• responses_404 - Number of requests that resulted in a 404 result code
• responses_other - Number of requests that resulted in a response code other than 200 or 404
• effectiveBps - The effective bandwidth for the test (bytes over the test time)
• effectiveBpsDoc - The effective bandwidth for the test until the document complete time (onLoad event)
• server_rtt - Estimated Round Trip Time to the server for the base page
• domTime - (deprecated) Time to the point where a specified DOM element appeared on the page

Visual Metrics

• render - Start render time. When the first onscreen content change happened based on the video capture data
• SpeedIndex - Histogram-based SpeedIndex calculated from video capture
• chromeUserTiming.LargestContentfulPaint - (Chrome Web Vitals Measurement) Time to the largest contentful paint
• chromeUserTiming.CumulativeLayoutShift - (Chrome Web Vitals Measurement) amount of content shift during the page load
• firstPaint - (also PerformancePaintTiming.first-paint) Browser-reported first paint time (from performance timing)
• firstContentfulPaint - (also PerformancePaintTiming.first-contentful-paint) Browser-reported first contentful paint time (from performance timing)
• firstImagePaint - Browser-reported first image paint time (from performance timing)
• lastVisualChange - Time of the last visual change of any kind based on the video capture
• visualComplete - When the page was 100% visually complete for the first time based on the video capture and comparing page histograms (SpeedIndex completeness)
• visualComplete85 - When the page was 85% visually complete for the first time based on the video capture and comparing page histograms (SpeedIndex completeness)
• visualComplete90 - When the page was 90% visually complete for the first time based on the video capture and comparing page histograms (SpeedIndex completeness)
• visualComplete95 - When the page was 95% visually complete for the first time based on the video capture and comparing page histograms (SpeedIndex completeness)
• visualComplete99 - When the page was 99% visually complete for the first time based on the video capture and comparing page histograms (SpeedIndex completeness)
• chromeUserTiming - A list of the raw chrome-reported blink and rail timing events
• chromeUserTiming.LargestImagePaint - Chrome-reported largest image paint (subset of largest contentful paint)
• chromeUserTiming.LargestTextPaint - Chrome-reported largest text paint (subset of largest contentful paint)
• chromeUserTiming.firstContentfulPaint - Chrome-reported first contentful paint
• chromeUserTiming.firstImagePaint - Chrome-reported first image paint (subset of first contentful paint)
• chromeUserTiming.firstTextPaint - Chrome-reported first text paint (subset of first contentful paint)
• chromeUserTiming.firstPaint - Chrome-reported first paint time
• LayoutShifts - Array of each time the page layout shifted. Includes the time of the shift, "score" (amount) of the shift and the cumulative layout shift score at that time
• firstMeaningfulPaint - (also chromeUserTiming.firstMeaningfulPaint, deprecated - use firstContentfulPaint) Chrome-reported calculation of when the browser first painted the "meaningful" content
• titleTime - (deprecated) Time until the page title became available
• aft - (deprecated) Above-The-Fold Time

Interactivity Metrics

• TotalBlockingTime - (Chrome Web Vitals Metric) Total amount of time where the main thread was blocked by long tasts after the initial content was rendered
• maxFID - The largest long-task after the initial content was rendered (longest time the user's input can be blocked)
• TimeToInteractive - The latest point where the page became Interactive and remained interactive for over 5 seconds
• LastInteractive - The latest point where the page became Interactive (may not have been interactive for the required 5 seconds)
• TTIMeasurementEnd - The end time of the measurements for interactive periods
• longTasks - List of the start and end times of all main-thread tasks that tool longer than 50ms
• interactivePeriods - (deprecated - use longTasks instead) List of all of the start and end times where the main thread was considered "interactive"

Javascript and CPU timings

• cpu.* - Main thread time spent by each category of timeline activity
• cpuTimes - Array of main-thread CPU timings by each category of timeline activity
• cpuTimesDoc - Array of main-thread CPU timings by each category of timeline activity that occurred before the document complete time (load event)
• fullyLoadedCPUms - CPU time used to load the page (reported by the OS)
• fullyLoadedCPUpct - Average CPU utilization percent to load the page
• v8Stats - V* runtime call stats (if enabled)

Page Information

• URL - URL that was used to start the test
• document_URL - Browser-reported URL of the final document
• document_hostname - Browser-reported hostname of the final document
• document_origin - Browser-reported origin of the final document
• final_url - Final URL navigated to by the browser
• base_page_cdn - Detected CDN used for serving the base page
• base_page_cname - CNAME for the hostname used for serving the base page (if there is one)
• base_page_dns_server - Authoratative DNS server used by the domain for the base page
• base_page_ip_ptr - Reverse IP lookup of the IP address that served the content for the base page
• detected - Raw output from Wappalyzer with the categories of content detected and the list of detected content (and their versions)
• detected_apps - Flattened list of Wappalyzer detected application versions by application name
• domElements - Number of DOM elements on the page
• bigImageCount - Number of "large" images on the page
• smallImageCount - Number of "small" images on the page
• maybeCaptcha - A possible Captcha challenge page was detected
• Images - List of the images on the page DOM including the image URL, dimensions and display dimensions
• breakdown - Array of the bytes and request counts by content type
• domains - List of domains used to load content, the number of requests, bytes and connections used as well as the CDN if one was detected.

Browser State

• browser_name - Name of the browser being used in the test (i.e. Chrome)
• browser_version - (also browserVersion) Version string for the browser (i.e. 85.0.4183.102)
• Colordepth - Screen color depth as reported by the browser
• Dpi - Screen DPI as reported by the browser
• Resolution - Screen resolution of the test machine as reported by the browser
• cached - 1 for repeat view tests, 0 for first view

Lighthouse Summary Metrics

• lighthouse.Accessibility - Lighthouse Accessibility score (0-1)
• lighthouse.BestPractices - Lighthouse Best Practices score (0-1)
• lighthouse.ProgressiveWebApp - Lighthouse PWA score (0-1)
• lighthouse.SEO - Lighthouse SEO score (0-1)
• lighthouse.Performance - Lighthouse Performance score (0-1)
• lighthouse.Performance.cumulative-layout-shift - Cumulative Layout Shift as reported by Lighthouse
• lighthouse.Performance.first-contentful-paint - First Contentful Paint as reported by Lighthouse
• lighthouse.Performance.interactive - Time to Interactive as reported by Lighthouse
• lighthouse.Performance.largest-contentful-paint - Largest Contentful Paint as reported by Lighthouse
• lighthouse.Performance.speed-index - Speed Index as reported by Lighthouse
• lighthouse.Performance.total-blocking-time - Total Blocking Time as reported by Lighthouse

Optimization Checks/Grades

• optimization_checked - 1 if the optimization checks were run as part of the test (0 otherwise)
• score_cache - Score for caching static content (0-100)
• score_cdn - Score for using a CDN for static content (0-100)
• score_compress - Score for properly compressing lossy images (JPEG 85 reference point)
• image_savings - Byte savings for properly compressing images
• image_total - Total image bytes
• score_gzip - Score for properly compressing text content
• gzip_savings - Byte savings for properly compressing text content
• gzip_total - Total text content size
• score_keep-alive - Score for properly using keep-alive when more than one request is made to a given origin
• score_progressive_jpeg - Score for using progressive JPEGs
• score_etags - (deprecated)
• score_cookies - (deprecated) Score for not setting cookies on domains for static resources
• score_combine - (deprecated) Score for combining separate JS files
• score_minify - (deprecated) Score for the minification check for Javascript and HTML
• minify_savings - (deprecated) Byte savings possible (pre-compression) by minifing script and HTML
• minify_total - (deprecated) Total size of content that is subject to minifying

Instrumented Metrics

• userTime - Time of the last user timing mark event
• userTime.* - Latest timestamp for each user timing mark
• userTimes - Array of user timing marks and their timestamps
• userTimingMeasure.* - Duration for each user timing measure
• userTimingMeasures - Array of user timing measures (includes start times and durations)

Test Information

• result - Test result (0 and 99999 are success, anything else is a failure)
• eventName - Name of the test event step (for multi-step tests)
• tester - ID of the test machine that ran the test
• date - Epoch time (in ms) when the test was started
• numSteps - Number of steps in the test (for scripted tests)
• run - Run number in the case of a multi-run test
• step - Step number of the current step
• test_run_time_ms - Amount of time it took to run the test and process the data
• start_epoch (deprecated) - Epoch time when the test was started

Misc

• blinkFeatureFirstUsed - Array of all of the blink features that were detected and when that feature was first used. Includes the freture name and number
• consoleLog - Array of console log messages including the message text, level and message source
• custom - List of the names of the custom metrics (individual metrics will be recorded at the top-level)
• main_frame - ID of the main frame
• videoFrames - Information about each unique video frame for the video of the page load. Includes URL to the video frame image, timestamp and the calculated visual completeness
• final_base_page_request - Index number of the request that was the request for the base page (after redirects)
• final_base_page_request_id - Request ID of the request that was the request for the base page (after redirects)