Google Lighthouse v6 is out now !
Webpagetest.org includes Google Lighthouse tests if you choose to enable them as outlined here. Which is same as Google PageSpeed Insights.
Note Google Lighthouse v6’s scoring metrics have changed with removal of First CPU Idle and First Meaningful Paint and addition of Total Blocking Time, Largest Contentful Paint and Cumulative Layout Shift and also changes to the score weighting to further emphasize the impact of excessive Javascript. See Lighthouse performance scoring
Lighthouse 5 Audit Weight
- First Contentful Paint 20%
- Speed Index 27%
- First Meaningful Paint 7%
- Time to Interactive 33%
- First CPU Idle
Lighthouse 6 Audit Weight
- First Contentful Paint 15%
- Speed Index 15%
- Largest Contentful Paint 25%
- Time to Interactive 15%
- Total Blocking Time 25%
- Cumulative Layout Shift 5%
As you can see previously Time To Interactive was weighted at 33% of the total score in Lighthouse v5 so even if you had alot of Javascript slowing Time To Interactive, if you had a good First Contentful Paint (20%) and Speed Index (27%) which totaled 47% of the score, you could still get a relatively high Lighthouse score.
However, with Lighthouse v6 the weighting has changed. They have lowered the weighting on First Contentful Paint (15%) and Speed Index (15%) which totaled 30% of the score. And increased weighting on metrics that Javascript impact such as Time To Interactive (15%) and Total Blocking Time (25%) and Cumulative Layout Shift (5%) which have a combined 45% weighting to the overall score.
This means if your web site is Javascript heavy, you’d expect lower Google Lighthouse v6 scores in Webpagetest and Google PageSpeed Insights v6.