I changed my site! Why did the Speed or Optimization score not change?
The speed data shown in PSI is not updated in real-time. The reported metrics reflect the user experience over the trailing thirty days and are updated weekly. For the Optimization score, PageSpeed Insights caches results for a short period of time and any changes you've made to implement suggested optimizations should be recognized within a few minutes.
Why am I not seeing any speed data for a URL?
PSI uses data from the Chrome User Experience Report, which provides speed data for popular URLs that are known by Google's web crawlers. If the speed data for the queried URL is not available in the CrUX dataset, we recommend using Lighthouse to run a synthetic performance audit to estimate page speed, and investigate page optimization recommendations provided by PSI and Lighthouse.
How does this differ from the Chrome User Experience Report?
PageSpeed Insights incorporates data from the Chrome User Experience Report to provide real-world performance information for sites, as captured by FCP and DCL. The performance data in both CrUX and PSI is generated by real users in the wild and represents how users experience the web.
Why does PSI use FCP and DCL? Which one is the most important?
First Contentful Paint (FCP) measures when a user sees a visual response from the page. Faster times are more likely to keep users engaged. DOM Content Loaded (DCL) measures when HTML document has been loaded and parsed. Faster times have been shown to correlate with lower bounce rates. We encourage you to look at a variety of metrics, including FCP and DCL to understand the performance of your page.
Where do the PageSpeed Insights performance optimizations come from?
PageSpeed Insights uses a variety of best practices from the web performance community. The optimization analysis fetches a site with a Blink renderer (the rendering engine that powers Google Chrome) that emulates both mobile and desktop devices.
Should I implement all of the optimization recommendations?
Since PageSpeed is a performance optimization tool, its recommendations are biased in favor of speed. However, we recognize that web development is complex, and our suggestions might be restrictive for an individual web site. You have to consider the tradeoffs for your own application: some of PageSpeed's recommendations take substantial effort to implement, so you need to evaluate the cost of making changes vs. the benefit the rule would have on your page. Our goal is simply to point out the issues that you should consider fixing.
Why am I seeing a captcha?
PageSpeed Insights may occasionally show a captcha to confirm you are not a bot. If you are encountering a captcha when using the API, it may be due to the fact that you are using a shared API key. You can acquire an individual API Key by following these instructions.