PageSpeed Insights, now powered by Lighthouse

Monday, November 12, 2018

At Google, we know that
speed matters
and we provide a
variety of tools to
help everyone understand the performance of a page or site. Historically, these tools have used
different analysis engines. Unfortunately, this caused some confusion because the recommendations
from each tool were different. Today, we’re happy to announce that Pagespeed Insights (PSI) now
uses
Lighthouse as its analysis engine. This
allows developers to get the same performance audits and recommendations everywhere: on the web,
from the command line, and in Chrome DevTools. PSI also incorporates field data provided by the
Chrome User Experience Report
(CrUX). Version 5 of the PageSpeed Insights API will now provide CrUX data and all of the
Lighthouse audits. Previous versions of the PSI API will be deprecated in six months.

PageSpeed Insights provides the following information:

• 
  Lab Data
  :
  PSI fetches and analyzes the page using
  Lighthouse, which simulates how a mobile
  device loads a page. It computes a set of
  performance metrics
  for the page (such as First Contentful Paint and Time to Interactive) and summarizes these
  metrics with a performance score from 0-100. Scores are categorized into three levels; 90 and up
  is considered to be a good score.
• 
  Field Data
  : PSI also displays real-world performance metrics (First Contentful Paint and First
  Input Delay) for the page and its
  origin.
  (As a result, we’ve also deprecated the origin: query in PSI). Note that not all sites may have
  field data available for display. The data set relies on a version of the Chrome User Experience
  Report that is updated daily and is aggregated over the previous 28 days. Keep in mind that the
  metrics here may be different from the ones in the Lab Data section as they capture a wide
  spectrum of real-world network conditions and devices used by Chrome users.
• Opportunities: PSI provides suggestions on how to improve the page’s
  performance metrics. Each suggestion in this section estimates how much faster the page will
  load if the improvement is implemented.
• Diagnostics: This section provides additional information about how a page
  adheres to best practices for web development.

The
PSI v5 API
now returns this new analysis together with CrUX data, and all Lighthouse category data
(Performance, Progressive Web App, Accessibility, Best Practices, and SEO) for a given URL.

We have more information about the changes in our
FAQ.
If you have a specific, answerable question about using PageSpeed Insights, ask the question in
English on
Stack Overflow.
For general questions, feedback, and discussion, start a thread in the
mailing list.

Posted by Rui Chen and Paul Irish, PageSpeed Insights and Lighthouse teams