PageSpeed (Legacy)
YSlow (Legacy)


Speed is a crucial aspect in providing a pleasant user experience to visitors of your site. It ensures that a visitor's limited attention span and time are spent on actual content and not wasted waiting for images and scripts to load. Speed is even more important for mobile device users, as studies have shown that users are unlikely to tolerate more than a 3 second page load time on a mobile device. If your site fails to offer a quick response, your users will leave.

In terms of SEO, Google already uses 'Page Speed' in their ranking algorithm, and plan to include 'Page Experience' as well. Google has also announced that high-performance pages will henceforth be marked as 'Fast pages'. As developers and marketers look to optimize their sites, Page Speed and Page Experience should be among the top optimizations to consider.

Despite this, however, Google has made it clear that even though Page Speed and Page Experience are important, they will continue to prioritize pages with the most relevant and quality content overall.

Therefore, don't do it just for SEO, do it for your users!

The complexity of modern websites necessitates a nuanced approach to analyze site performance. GTmetrix uses Google's Lighthouse - the standard in web performance to assess your website's performance and provide insights and actionable recommendations.


Google Lighthouse is an open-source tool for providing web performance insights for your website. We've integrated it into our testing platform to provide a comprehensive, easy-to-understand report.

Lighthouse focuses on user-centric metrics. That means our tests measure a number of user-centric metrics that reflect what your site visitors would actually experience as your page loads.

This helps you develop a website that is not only loading fast but also feels fast in the perception of your visitors. We encourage you to learn more about these metrics and audits through our detailed documentation. We also provide simplified guidance on what you should focus on, in the interest of optimizing the website experience for your visitors.

Note that our Legacy Reports (including API v0.1 reports) use Google's former PageSpeed tool and Yahoo's YSlow tool.

PageSpeed and YSlow (Legacy Reports)

GTmetrix also offers performance analysis based on PageSpeed and YSlow recommendations for Legacy Reports. PageSpeed and YSlow are older libraries that provide recommendations representing general front-end best practices you can apply for optimizing your website. Your page is scored on how well it is built and adheres to these best-practices.

While many of the PageSpeed/YSlow recommendations tracked in the Legacy Reports are still valid practices for performance optimization, note that some of these recommendations may be deprecated and not applicable to your website's specific implementation.

Lighthouse metrics serve to be a better indicator to analyze your website's performance from both a user-experience and a front-end structure standpoint.

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