PageSpeed ​​Insights adds new Lighthouse speed metrics

ByDavid M. Conte

May 12, 2022

Google’s PageSpeed ​​Insights has added two new metrics to the PageSpeed ​​Insights API and UI for Lighthouse. The two experimental labeled parameters are now collected for field data while the corresponding laboratory data can be used for diagnostic purposes.

Updated Google Flagship

Lighthouse is now updated with the two new measurements.

The new Lighthouse metrics are:

  • Interaction with the following paint (INP)
  • Time to first byte (TTFB)

Time to first byte (TTFB)

Many people are already familiar with Time to First Byte, it has been around for many years and some may already be familiar with it.

The Time to First Byte (TTFB) metric measures how quickly the server responds to a resource request.

So, the significance of this metric is that it helps isolate one factor (server responsiveness) that can have a negative effect on all other page load metrics that come after it.

This makes TTFB a very important measurement to look at for diagnostic purposes.

Anyone focused on improving Core Web Vitals should check out TTFB for a possible quick win.

What has changed about TTFB is that this is the first time it has been available as a metric in the results section of PageSpeed ​​Insights.

Chrome will also collect and report TTFB terrain data for the first time.

Interaction with the following paint (INP)

Next Paint Interaction (INP) is a brand new metric that represents the time it takes to interact with the entire page, what Google calls the “global interaction latency.”

INP metrics represent the time it takes to interact with the entire page, unlike First Entry Delay which only measures how long it takes for the page to respond to a site visitor’s first interaction.

Google uses a sample shopping page to illustrate the difference between a good INP and a bad INP.

The example of a shopping page shows a clickable image that generates a larger zoomed-in version.

An example of poor responsiveness is a user clicking on the image and then waiting for something to happen while the larger image downloads to the browser. There is no feedback response to the click.

An example of good responsiveness is when a user clicks on the same image and immediately responds with a page load graphic that indicates the image request has been received and is loading .

Screenshot of good responsive web page element

The above is an example of how the new INP metric will measure all responsive elements on a web page to arrive at a representation of interaction with Next Paint.

Google’s Web.dev explains the new Interaction to Next Paint (INP) metric:

“INP is a metric that aims to represent the overall interaction latency of a page by selecting one of the longest interactions that occur when a user visits a page.

For pages with less than 50 total interactions, INP is the interaction with the worst latency.

For pages with many interactions, INP is most often the 98th percentile of the interaction latency.

New PageSpeed ​​Insights layout

Both new metrics are available for review now in the PageSpeed ​​Insights tool.

But it may take a while for the field data to show, because the field data comes from real Chrome browser users who have opted in to allow page speed data to be sent to Google for visiting the site and recording their data.

The main Web Vitals scores are listed first in a row (on desktop view).

Lighthouse then displays a second line of statistics:

  • Happy first paint
  • PNI
  • TTFB

Screenshot of the new Lighthouse metrics display

Featured Metrics

Chrome headlight extension

Another way to view new metrics is with the Chrome Lighthouse extension.

The way to use it is to navigate to any page and a square box in the top right of the browser will turn red or green depending on whether the page passes the Core Web Vitals metrics or not.

Clicking on the box itself activates a display of the CWV and experimental measurements.

Screenshot of Chrome Lighthouse extension

Chrome headlight extension

New metrics available in third-party tools

The many page speed tools that use Lighthouse in their analysis will also show INP and TTFB metrics.

For example, WebPageTest.org now displays the new metrics.

Screenshot of WebPageTest Lighthouse results

Screenshot of results from WebPageTest.org showing reported TTFB and INP measurements

Updates to page speed information

There are also additional updates to the PageSpeed ​​Insights tool.

A noticeable change is the speed at which results are displayed, which is accomplished by loading field and lab data in parallel.

Another change is that PageSpeed ​​Insights will first try to resolve HTTP redirects before sending them to Lighthouse for analysis. Previously, Lighthouse handled HTTP redirects when crawling.

Plus two other additional changes:

“Core Web Vitals (CWV) metrics (LCP, FID, CLS) appear directly below the CWV rating.

We’ve tightened up the design, reducing verbosity and vertical space.

Lighthouse data is more useful

Adding these two metrics, TTFB and INP, makes all page speed tools that use Lighthouse analysis much more useful. TTFB provides feedback on server-related issues that may be causing poor speed performance elsewhere and INP provides a broader view of page performance than was previously available.

Quotes

Read the official Google INP explainer

Interaction with the following paint (INP)

Read Google’s Recently Updated TTFB Explainer

Time to first byte (TTFB)

Read the PageSpeed ​​Insights release notes

Release Notes for PageSpeed ​​Insights API and PageSpeed ​​Insights UI