Google Lighthouse is a modern, comprehensive real-world web app performance auditing tool based on Chrome User Experience BigQuery data reports.
Google Lighthouse 6 Release Page | Google Lighthouse 6 Changelog
Changes and updates in
Google Lighthouse 6 will be implemented in SpeedFactor in the upcoming weeks.
Google Lighthouse 6 just landed and it measures eight performance-related metrics in the Performance Section of the report with the following Lighthouse performance weighting: New in Google Lighthouse 6
(LCP) is a new metric that measures the time from navigation until the largest content element in the viewport is rendered ( Largest Contentful Paint #9905, #10213, #10452, #10529).
largest-contentful-paint-element is a companion audit that gives information about which element triggered the LCP (
#10517, #10713). (CLS) is a new metric that measures the amount of unexpected movement of content as a page loads ( Cumulative Layout Shift #9037, #10427, #10495, #10570, #10728).
layout-shift-elements is another companion diagnostic that gives information about the elements that shifted as the page loaded (
#10702). Google Lighthouse Performance Metrics:
What is First Contentful Paint [FCP]?
First Contentful Paint is the moment when the browser paints first content on the screen.
First Contentful Paint metric insides:
First Contentful Paint score has the weight of 20%. The user must see the page ‘appearing’ within the first second after request. The text, logo, icons, canvas or navigation bar contours are considered the FCP. The ‘above-the-fold’ CSS styles are considered critical CSS and must be loaded in the head. What is First Meaningful Paint [FMC]?
First Meaningful Paint is the moment when page’s primary above-the-fold layout change has happened and meaningful content appeared on the screen.
First Meaningful Paint metric insides:
First Meaningful Paint score has the weight of 20% Full-width hero images usually take longer to download and render comparing to headline and above-the-fold text. Non-responsive full-width images are one of the most common reasons for the awful First Meaningful Paint delay. First Meaningful Paint metric requires the web fonts loaded. What is Page Speed Index [PSI]?
Page Speed Index metric insides:
Page Speed Index score has the weight of 10%. The lower PSI time, the faster the page loads. The fewer styles and scripts the page content needs the lower PSI is. Page Speed Index depends on user device resources and capabilities. The PSI was initially introduced by WebPageTest.org. The Page Speed Index score is based on Speedline‘s open-source module. What is Time to Interactive [TTI]?
Time to Interactive (TTI) is the first moment when page useful content is loaded and is fully interactive to user actions.
Time to Interactive metric insides:
Time to Interactive grades:
0 – 2.2 seconds – ‘excellent’ TTI score. 2.2 – 5 seconds – ‘fast’ TTI score. Over 7 seconds – ‘slow’. What is First CPU Idle [FCI]
First CPU Idle defines the moment the device’s CPU takes an idle state and awaits a user input.
First CPU Idle metric insides:
First CPU Idle score had the weight of 13%. First CPU Idle time is heavily dependent on user device resources and capabilities. First CPU Idle moment occurs when the user can start to interact with the page; TTI occurs when the user is fully able to interact with the page. Since First CPU Idle moment is nearly identical to the Time to Interactive moment, the First CPU Idle metric has been deprecated in Lighthouse 6.
First CPU Idle grades:
0 – 3 seconds – ‘excellent’ CPU Idle score. 3 – 4.7 seconds – ‘fast’ CPU Idle score. Over 6.5 seconds – ‘slow’ score. What is Max Potential First Input Delay [FID]?
Max Potential First Input Delay audits estimated input latency during the busiest 5-second window of page load. FID measures how fast the app responds to a user input.
Max Potential First Input Delay metric insides:
Total Blocking Time measures the total amount of time the page stays is unresponsive to user inputs.
Total Blocking Time metric insides:
Total Blocking Time grades:
0-300ms TBT time is considered ‘fast’. 300-600 TBT time is considered ‘moderate’. Over 600ms TBT time is considered ‘slow’. What is the Largest Contentful Paint [LCP]?
Largest Contentful Paint is a moment when the largest above-the-fold content element is visible in the viewport and the page looks useful.
Largest Contentful Paint metric insides:
The Largest Contentful Paint metric has been introduced in Lighthouse 6. LCP considers the following page elements: img, image, video, divs with background images, etc. Largest Contentful Paint is a user-centric metric for measuring perceived load speed. Native support for LCP launched in Chrome 77. Lighthouse extracts LCP data from Chrome’s tracing tool.
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