New performance metrics, updates to PageSpeed Insights and Chrome User Experience Report (CrUX), and more.
En Chrome Developer Summit, Paul Irish y yo anunciamos actualizaciones de Lighthouse — Lighthouse CI, una nueva fórmula de puntuación de rendimiento y más. Junto con las grandes noticias de Lighthouse, presentamos emocionantes desarrollos de herramientas de rendimiento que incluyen nuevas métricas de rendimiento, actualizaciones de PageSpeed Insights y Chrome User Experience Report (CrUX), y conocimientos del análisis de Web Almanac del ecosistema web.
New performance metrics
Medir los matices de la experiencia de un Username es la clave para cuantificar el impacto que tiene en sus resultados y realizar un seguimiento de las mejoras y regresiones. Con el tiempo, han evolucionado nuevas métricas para capturar esos matices y llenar los vacíos en la medición de la experiencia del usuario. La última incorporación a la historia de las métricas son dos métricas de campo: la pintura con contents más grande (LCP) y el cambio de diseño acumulativo (CLS), que se están incubando en el W3C Web Performance Working Group, y una nueva métrica de laboratorio: el tiempo total de bloqueo (TBT).
Larger Content Paint (LCP)
Largest Content Paint (LCP) reports when the largest content item becomes visible in the viewport.
Before painting with larger content, First Significant Paint (FMP) and Speed Index (SI) were used to capture the loading experience after initial painting, but these metrics are complex and often do not identify when the main content of the page has been loaded. Research has shown that simply looking at when the largest element on the page is rendered best represents when the main content of a page loads.
La nueva métrica de Pintura con contenido más grande pronto estará disponible en los informes Lighthouse y, mientras tanto, puede medir LCP en JavaScript.
Total Block Time (TBT)
The Total Blocking Time (TBT) metric measures the total amount of time between First Contentful Paint (FCP) and Time to Interactive (TTI) where the main thread was blocked long enough to prevent input response.
A task is considered long if it runs on the main thread for more than 50 milliseconds. Any millisecond above that is counted towards the lock time for that task.
The total lock time for a page is the sum of the lock times for all long tasks that occurred between FCP and TTI.
Mientras que Time to Interactive hace un buen trabajo al identificar cuándo el hilo principal se calma más adelante en la carga, el tiempo de bloqueo total tiene como target cuantificar qué tan tenso está el hilo principal durante la carga. De esta forma, TTI y TBT se complementan y proporcionan equilibrio.
Cumulative Design Change (CLS)
Cumulative Design Change (CLS) measures the visual stability of a page and quantifies how often users experience unexpected design changes. Unexpected content movement can be very frustrating, and this new metric helps you address that problem by measuring how often it occurs for your users.
A screencast illustrating how design instability can negatively affect users.
See the detailed Cumulative Design Change guide for how it is calculated and how to measure it.
Lighthouse's new performance scoring formula will soon downplay FMP and FCI and include the three new metrics, LCP, TBT, and CLS, as they better capture when a page feels usable.
See the Lighthouse performance score and the new collection of metrics from web.dev for more information.
Field Data Thresholds (CrUX) Adjusted in PageSpeed Insights
For the past year, we have been analyzing web performance from the field through Chrome user experience
(CrUX) data. Using the statistics from that data, we reevaluated the thresholds we use to label a website as "slow," "moderate," or "fast" in field performance.
The term "average" that used to describe sites that fall between "slow" and "fast" is now changed to "moderate", which is more appropriate since this middle group was not related to a statistical average.
To get a general evaluation of a site, PageSpeed Insights (PSI) uses a certain percentile of the total field data distribution as the gold number for that site; The previous thresholds used were the 90th percentile for the first painting with content and the 95th percentile for the first-entry delay (FID).
Por ejemplo, si un sitio tiene una distribución de FCP de 50% rápido, 30% moderado, 20% lento, el percentil 90 de FCP está en la sección lenta, lo que hace que la puntuación de campo general del sitio be lenta.
This has been adjusted to have a better overall layout on the websites and the new breakdown is:
| Metric | General percentile | Fast (ms) | Moderate (ms) | Slow (ms) |
| FCP | 75th percentile | 1000 | 1000-3000 | 3000+ |
| DEFENDER | 95th percentile | 100 | 100-300 | 300+ |
For example, now if a site has a FCP distribution of 50% fast, 30% moderate, 20% slow, the FCP 75th percentile is in the moderate section, making the site's overall field score moderate.
Redirecciones de Url canónicas en PageSpeed Insights
Para permitirle medir la experiencia del usuario con la mayor precisión posible, el equipo de PageSpeed Insights ha agregado un mensaje de reanálisis a PSI. Para los sitios que se redirigen a una nueva URL, se le solicita que vuelva a ejecutar el informe en la Destination url para obtener una imagen más completa de su rendimiento real.
CrUX in the new search console speed report
Search Console lanzó su new speed report
a week before Chrome Dev Summit. It uses data from the Chrome User Experience Report to help site owners discover potential user experience issues. The speed report automatically assigns groups of similar URLs into "Fast", "Moderate" and "Slow" groups, and helps prioritize performance improvements for specific problems.
Web Almanac
In the opening speech we announced the launch of the Web Almanac, an annual project that combines statistics and trends on the state of the web with the experience of the web community. 85 contributors, comprised of Chrome developers and the web community, have volunteered to work on the project, which looks at 20 core issues about the web that address how sites are built, delivered, and experienced. Start exploring the Web Almanac to learn more about the status of your performance, JavaScriptand third code on the web.
Learn more
For more details on the Chrome Developer Summit performance tool updates, watch the speed tools evolution talk:
