PageSpeed Insights and the API have been updated to now show more field data than before. The updated PageSpeed Insights scoring is live and should reflect the new way of handling field data.
PageSpeed Insights previously only displayed the field data if all of the field data was collected.
This was problematic because 30% of web pages don’t record one of the metrics, First Input Delay (FID).
Field Data in PageSpeed Insights
Field data is the page speed metrics of real users that Google collects through Chrome mobile browsers that have opted-in to sending anonymized performance information from site visitor’s actual experience on a web page, which is then used for calculating the page speed metrics.
Lab data is what is used in Google Lighthouse, a tool that is used to estimate what a PageSpeed score may be.
Lighthouse ships in the Chrome browser and powers the dev tools.
Right clicking any where on a web page opens up Chrome Dev Tools and from there Lighthouse can be used to simulate what the PageSpeed metrics are.
But these are only simulations, estimates, of what the values may be.
The actual data that Google may use for ranking purposes is called Field Data and that’s the data that is collected from real users downloading actual pages on mobile devices under real circumstances.
Available Field Data is Now Shown
The change Google made in the PageSpeed Insights API and the tool is that Google will show the field metrics that have been collected, even if other field data has not been collected.
Previously Google would only report if all the data that has been collected met a specific threshold of data.
According to Google’s Rick Viscomi on Twitter, he calls this a big deal because the missing data happens to 30% of origins in the Chrome User Experience Report where the First Input Delay data is missing, while the other data was there.
“Previously you’d see “no data” if you were just missing FID data. Now you’ll see whatever is available.
This is a big deal because ~30% of origins in CrUX were missing FID data!”
Why Does First Input Delay (FID) Go Missing?
First Input Delay is a metric that measures the responsiveness of a website by measuring the delay in processing an event like clicking a button, tapping on a menu or entering data with a keyboard press and the time it takes for the web page to respond.
Scrolling and zooming in on text or images do not count as an interaction with the web page.
According to Google’s Web.dev page on FID, many users do not interact with a web page and for that reason the Chrome User Experience Report (CrUX) will not have this metric recorded.
“Not all users will interact with your site every time they visit. And not all interactions are relevant to FID…
…FID is a metric that can only be measured in the field, as it requires a real user to interact with your page.”
Rick Viscomi explained in a follow up tweet why First Input Delay (FID) tends to go missing:
“FID is especially prone to be absent because, unlike other Web Vitals, it relies on a user interaction to be measured. Nearly all page views incur an LCP or CLS, but not all of them have user interactions!”
This is a positive step from Google because the additional information will allow more publishers to make better decisions on what needs to be fixed in relation to PageSpeed metrics.
This is how Google’s official announcement explained it:
“PageSpeed Insights field data is now provided for pages and origins that might have insufficient data for a metric, but sufficient data for other metrics.
Previously, field data was only surfaced if all metrics for a page or origin met a threshold of data.
Now, any metric that meets the data threshold will be provided.
This is reflected in the loadingExperience and originLoadingExperience objects in the API, and also in the frontend.”
Good News for Web Publishers, Developers and SEOs
This is great news for publishing community because field data reflects the actual site visitor user experience on a web page.
The more field data information publishers have the more accurate and complete action can be taken to fix real world problems.
Video Illustrating How First Input Delay is Measured
Release Notes for PageSpeed Insights API and PageSpeed Insights UI
Differences Between Field Data in PSI and CrUX
Google Web.dev Page on First Input Delay (FID)
What If a User Never Interacts With Your Site?
PageSpeed Insights API Documentation