How reliable is Google analytics page loading insights?

[Nat]

Had a mild panic attack when I saw the page load time in Google analytics. I've never checked this before, I always use tools.pingdom.com... but the G analytics are showing load times that are 3 seconds slower for one site.

Idk if it matters, but I put the G code in the footer instead of the header since I care more about page render than analytics.

 

[Jared]

I've always wondered . . .

Does Google actually measure your site's speed, and use that result in its algorithm, or does it simply rely on the side effects of a slow site, like a high bounce rate?

 

[Ryuzaki]

Does Google actually measure your site's speed, and use that result in its algorithm, or does it simply rely on the side effects of a slow site, like a high bounce rate?

I feel confident that they measure each page.

Regarding what Google Analytics shows, not sure at all. But if you run a query in Webmaster Tools to render a page an GoogleBot sees it, you'll notice that they do ignore asynchronous and slow display ads. My guess is this doesn't factor into your page speed in regards to the algorithm. But as Jared points out, it will impact your user metrics.

From here: https://support.google.com/analytics/answer/1205784?hl=en

• Page-load time for a sample of pageviews on your site. You can view the data across different dimensions to see how quickly your pages loaded from a variety of perspectives (e.g., in different browsers, in different countries). Data is available in the Page Timings report.
• Execution speed or load time of any discrete hit, event, or user interaction that you want to track (e.g., how quickly images load, response time to button clicks). Data is available in the User Timings report.
• How quickly the browser parses the document and makes it available for user interaction. No additional configuration is required to see this data. Data is available in the Page Timings report, on the DOM Timings subtabs.

DOM Timing is going to be what matters. It won't include operating systems, people's slow internet speeds, browsers chock full of add-ons, etc.