Google’s John Mueller recently stated that Lighthouse metrics are an indication of how fast a site performs for actual users.
They’re not necessarily an indication of how Google’s algorithms assess a site with regards to speed.
This topic came up during a Google Webmaster Central hangout where the following question was asked:
“We have good First Meaningful Content at 2 seconds, but our Time to Interactive is 12-15 seconds which is affected by a large amount of scripts… according to Lighthouse even though it loads very fast for users.
We’re about to launch a new website and we wonder if it’s crucial to fix this before launch, or can it wait a few months?”
In response, Mueller says Lighthouse metrics are presented from the user-facing side of things.
From a search perspective, Google uses a variety of metrics to figure out how it should judge site speed.
However, with regards to SEO, Mueller says it’s better to get feedback from users rather than trying to determine if Google thinks a site is too slow.
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It sounds like Lighthouse aims to measure how fast a site loads for real users, but nothing beats actually asking them.
Mueller concludes his answer by saying if users think a site loads pretty fast, then that site is probably in a good state.
Conversely, I would imagine the opposite is also true. So listen to users if they say your site is too slow.
Hear the full question and answer below, starting at the 11:03 mark:
“So a lot of these metrics that you’re looking at from Lighthouse are primarily presented to you with regards to the user-facing side of things.
From our point of view, from a search point of view, we take a variety of these metrics together to figure out how we should be seeing this site with regards to speed.
The absolute measurements that you see there in Lighthouse are things that most likely have a stronger affect on how users see your site.
So instead of asking Google, with regards to SEO, “is this site too slow?” I would look at it with users and get their feedback instead.
If you’re saying that your site is actually pretty fast for users, and it provides the content fairly quickly, then probably you’re in a good state there.”