How Does Google Rate Your Website's Performance?

Search Engine Ranking Factors Change Frequently

Google considers a myriad of factors to decide how highly any page on your website should rank for any given search term. As the way in which we access the internet changes, and as users' expectations also change, so too do the importance of each of these factors. Amongst other changes, over the last two years we have seen the "mobile-friendliness" of websites go from being a minor factor in search engine rankings to a factor that will now significantly affect the success of any website.

Page Speed As a Ranking Factor

The search engine giant already considers page speed (the speed with which a web page loads in the user's browser) to be a ranking factor on all devices, but it will become a more important factor in the near future, particularly for searches performed on mobile, as previously hinted by Google's Gary Illyes. Nearly half of all visitors will leave a mobile site if the page doesn't load within 3 seconds according to Forrester Consulting, but in this case page speed does not necessarily refer to a difference in loading time that you can perceive, but rather imperceptible differences that may affect bandwidth and resource requirements more than user experience.

As cited by Google, web pages should minimize the amount of data they need send to the user, particularly on repeat visits to the same website, so as to minimize bandwidth and the associated costs. If every website followed best-practices for page speed, the internet as a whole would be much faster, costs to internet providers would fall, and far less energy would be required.

Using Google's Page Speed Insights Tool

Presumably with a view to making page speed a more important ranking factor in the near future, Google has developed a Page Speed Insights tool that will analyze your website's performance on mobile and desktop devices, with in-depth analysis of factors affecting your website's loading speed. You should visit the tool and enter your website's homepage for analysis. Once Google has analyzed your homepage you will be presented with your score for three key factors, as well as the option to receive more details by email:

Using Google's Page Speed Insights Tool

The email report you receive from Google will include details of why Google has rated your website the way it has:

Understanding Your Website's Rating

Understanding Your Website's Mobile Friendliness Rating

Google rates your website's user experience on mobile-sized screens to create this score:

  • Avoid plugins: These help the browser display special kinds of content such as Flash movies. Most plugins are not supported by mobiles and when they do, they are responsible for most problems viewing websites.
  • Configure the viewport: When a viewport is not specified, mobile devices will display the page at a typical desktop screen size, meaning that it will usually be almost impossible to read without zooming.
  • Size content to viewport: When a viewport is specified, some websites will be sized wider than the screen width, meaning that the user has to horizontally scroll to see the full page.
  • Size tap targets appropriately: When tap targets are not sized appropriately, this means that two or more links on the page are so close together that the user might accidentally follow the wrong link, creating a poor user experience.
  • Use legible font sizes: If the font sizes on your website are too small, users will find it difficult to read your content.

Understanding Your Website's Speed Rating

Google uses the same factors to determine your rating for Mobile Speed and Desktop speed. However, when these factors are the same for both devices they result in a poorer score for Mobile Speed than Desktop Speed because mobile users generally have less computing power and have also been shown to have less patience:

  • Avoid landing page redirects: If the URL pointing to your website in search results redirects more than once to the final landing page, this uses unnecessary resources and causes delay. Redirections should be able to be accomplished in just one step.
  • Enable compression: All modern browsers support "gzip compression" of websites, which can reduce the size of the files being transferred by up to 90%, with obvious effects on the loading speed.
  • Leverage browser caching: For repeat visitors to websites, it is not necessary for the browser to fetch a fresh copy of all the files associated with a web page unless they have changed. Enabling browser caching informs the browser if it can use the locally-stored copy of files the next time you access the website in your browser. Note that even if you enable caching for all your own website files, most websites also load resources from additional sources (such as Google Analytics),so it is not always possible to eliminate this factor from your score.
  • Minify CSS: Cascading Style Sheets (CSS) are commonly used to define the styles used to display a web page, but many such files contain a lot of unnecessary white space and commenting, which can be removed to decrease their file size.
  • Minify JavaScript: Many JavaScript files contain unnecessary white space and commenting, which can be removed to decrease their file size.
  • Minify HTML: The main structure of any web page is commonly defined by HTML code, but many HTML files contain a great deal of unnecessary white space and commenting, which can be removed to significantly decrease their file size.
  • Optimize images: Any format of images can and should be optimized for websites. There is usually no need to have very high-resolution images on websites.
  • Prioritize visible content: If the browser needs to load too many files to display the "above-the-fold" content of your website (the area the user sees first when your website loads) your website will score poorly for this factor.
  • Reduce server response time: Your website's host is responsible for it's server response time. Slow or highly variable response times are indicative of poor performance and in this case you should consider upgrading your host.
  • Eliminate render-blocking JavaScript and CSS in above-the-fold content: If JavaScript or CSS files are required to determine the layout of your website's "above-the-fold" content, you are likely to score poorly for this factor. However, it is worth noting that this is a highly complex factor and it is not always possible to improve this factor of your website's performance.


It is fair to say that is extremely unlikely that your website will score above 90 for all three factors, but you should aim to at least have a rating of "good" for each of the three sections. Ignoring poor scores in Google's own analysis of your website will inevitably lead to your website suffering from poorer search engine rankings in the future.