Why Is Site Speed Important for SEO & User Experience?

Most of us like getting things done now and it’s clear to understand why. In our society, we no longer have the luxury of taking our time. Technology has contributed to the creation of a world that’s moving at an impressive pace, but at the cost of our patience. We no longer wait in line and we certainly don’t wait for slow loading sites. The Internet may have become a more complex landscape of links and strategies, but the answer to the question “Is site speed important for SEO?” is still a resounding YES!

site speed importance

Did you know that impatient web users base their decisions on milliseconds? It seems hard to believe, but, as the NY Times reports, even 400 milliseconds is too long to wait. In fact, Microsoft computer scientist and speed specialist Harry Shum notes that 250 milliseconds is “close to the magic number now for competitive advantage on the Web.”

Site performance is so important that web users visiting your website will do so less often if it is more than 250 milliseconds slower than its competitors. Consequently, your SEO efforts should also be directed towards site speed and improving performance if you wish to keep up with your competition.

Why Improving Performance and Site Speed is Important for SEO

A page’s loading speed is among Google’s 200 ranking factors. In fact, both Google and Bing use this metric as a ranking factor. Normally, search engine spiders estimate this metric via HTML (based on a page’s file size and code). Additionally, Google also uses information collected via Chrome to better analyze account server speed, CDN usage as well as non-HTML-related speed signals.

Earlier this year, rumors claimed that Google was testing a red, “slow label” when displaying search results.

But how does Google actually measure site speed?

calculating page speed

A common assumption is that Googlebot is the one to measure page load. But that is hardly the case. Neither does it use information stemming from Page Speed analyzers to score a site’s performance. Instead, Google employs RUM (or real end-user monitoring) to check a website’s speed.

When users have the Google toolbar activated, data regarding page load time is sent back and used in the measuring process. By doing so, Google is actually accessing data collected via real bandwidths and users’ actual browsers.

Document Complete Time, Fully Rendered Time or TTFB?

Google isn’t keen on unveiling its secrets any time soon and it’s easy to understand why. After all, there’s no reason to offer the tools that would enable people to manipulate search engine ranking. So, right after the announcement was made that Google would incorporate page load time into its ranking factors, SEO’s began wondering which particular metric Google was referring to.

On the one hand, there’s “document complete time”. DCT (or document complete time) is the time that a browser requires to display a page with which you can interact with. It still needs to load additional content, but it loads as you begin clicking on or interacting with the page. “Fully rendered” time, on the other hand, refers to the time that is required for all content, images, advertisements and analytic trackers to load.

Moz’s Billy Hoffman attempted to find a correlation between these two metrics and a website’s search rank position. Curiously, though, they found no link between the time it takes for a page to be fully rendered and its search engine rank. The same was true for “document complete time”.

Another metric caught the spotlight, though. TTFB (or time to first byte) represents the time that is needed for a browser to receive the very first byte from the web server that hosts the particular site you’re accessing. For the first nine search rank positions, there was a clear correlation between an increasing TTFB (time to first byte) and a decreasing rank. Feel free to consult Hoffman’s findings here.

Google does offer some indications as to load time. The issue, though, is which particular metric is taken into consideration. The fact that Google takes load speed into account is logical: its highest priority is offering the best user experience when displaying certain search results. Slow load times are detrimental to user experience.

page load time affects abandonment rates

(Image courtesy of https://blog.kissmetrics.com/loading-time/?wide=1)

It should come as no surprise that a slow loading page is also a page that has low user engagement (and that is accompanied by all negative metrics that SEO’s fear: high bounce rates and a low average time on page). We already know that user behavior is strongly connected to how Google ranks certain pages. But it’s not just high bounce rates that decrease a slow-loading site’s rankings. Indexation is also affected when spiders cannot crawl a site properly.

Even if a page becomes almost fully interactive within three seconds, (and mind you that page abandonment increases exponentially the slower a page loads), Google may still consider it slow if it takes 10 seconds to be fully rendered.

According to this study published in the Journal of Web Engineering, crawl time also correlates with ranking position.

“Google seems to use the crawl time, i.e. time spent downloading a page by Google robot. A second set of experiments confirms that load time is not only correlated with the ranking position, but also effectively determines this position,” the study authors wrote.

Note that Google even measures non-crawlable pages for loading speed.

How to Measure Site Speed

It’s important to identify site performance optimization opportunities. You can use a multitude of tools and services that monitor and simulate your site’s performance and loading speed based on the actual visitors of that site.

Synthetic Measurement Services refer to those tools that simulate your site’s performance. Most of them are free and can be used to analyze both your site and that of your competitors.

  1. Google PageSpeed Insights

One great tool to use is provided by Google itself: PageSpeed Insights is an excellent solution to score your homepage and your site as a whole.

google insights page

After entering the URL, the analyzer will provide an overall PageSpeed Score for both mobile and desktop.

pagespeed insights

The same tool also analyses your user experience on a scale of 1 to 100 and offers suggestions as to which issues require your attention. Of course, you can run the same test on a specific page to see whether there are differences between it and your home page.

pageinsights mobile

  1. WebPageTest.Org

This service is widely used because the multiple of features that it offers. For one, you are able to perform URL-specific tests in accordance to multiple geographic locations, multiple mobile devices, browser types, connection types and clients that have enabled (or disabled) JavaScript.

web page test org

The test takes a bit to complete and your results will refresh as the test progresses. You may choose to perform the test for first view only or for first and repeat view. Aside from the load time, the tool also offers valuable information as to time to first byte, fully rendered time and total downloaded bytes.

WebPageSpeed Org

There’s also a content breakdown section:

webpagetest.org content breakdown

After the test is concluded, your site will get an overall grade reflecting its performance as well as suggestions on improving specific areas that need your attention.

page speed test

You can also use Google Analytics to track page load times and while that may offer valuable information, it seems that Google does not factor that data into search ranking.

  1. Yslow

This is a service designed by Yahoo! that also includes a nifty grading system and predefined rule sets. After running your site through Yslow, you will also receive improvement suggestions as well as a detailed performance analysis.

  1. Pingdom Website Speed Tool

Pingdom’s tests are performed on browsers, which means that your results will reflect real-world conditions better. Pingdom also compares your site’s speed against Yslow and Google Page Speed parameters, so that you can have a context to analyze your data in.

Real User Monitoring (RUM)

Unlike Synthetic Measurement Services, RUM offers insights that are based on your site’s actual visitors and the loading times they experience. You’ll have to add a bit of proprietary JavaScript code on the pages of your site and as such, RUM is not possible when attempting to evaluate your competition’s loading speed.

Think about it for a moment: RUM continuously gathers information from your site’s users, regardless of network, location or browser. When correctly used, RUM represents an invaluable tool that helps you analyze the way in which visitors use your site. You can learn about the thousands of Android and iOS devices used to access your site,

You can also identify how users move from page to page, so that you can later optimize the performance of those specific pages.

How to Improve Site Speed

Once you’ve examined your site’s speed and identified the issues you need to deal with, you’ll also have to correct them. There are basic things that you can do in order to improve your load time. You’ll want to target three areas:

  • Server
  • Content
  • CSS, JavaScript and Images

Be mindful, however, that making any major modification will require you to have a readily-available backup if something were to go wrong.


Everything starts with hosting. Suitable hosting will solve many load speed issues (or rather, prevent them). Whether you choose free web hosting or commercial hosting is up to you, remember, though, that there are pros and cons to each option.

While a free web host may impose advertising on your website and have web space limitations, it depends on individual hosts. Make sure to ask about FTP access, file size and file type limitations, reliability and bandwidth allotment. The same issues should be considered when opting for commercial hosting. Here are some tips on choosing a web host.

Browser caching is another option to consider, especially when your PageSpeed Insights results show that your server doesn’t include caching headers. Google has a series of recommendations where browser caching is considered, so make sure to have a look.

Data compression (especially GZIP compression) is another thing to factor in. Strive to always minimize the resources that browsers need to download. With the help of GZIP, a generic compressor, you can compress any stream of bytes, particularly text-based content. You can expect to achieve whopping compression rates (70-90%), however, when attempting to compress files that have already undergone compressing via other algorithms, results may not be as satisfying.

Keep alive signals are also efficient ways of reducing the latency of subsequent site requests. You’ll most likely have to contact your hosting provider and inquire as to this feature (more often than not, it is disabled).

The importance of content delivery networks (CDN) can’t be overstated. Basically, the closer a website’s server is to the user accessing the website, the faster data travels between the server and the visitor’s computer. So, logically, a visitor from Tokyo will experience longer load times when accessing a page as compared to a visitor from Miami (assuming that your servers are located in Miami). A CDN allows for foreign servers to store a copy of your website so that foreign users can also quickly access your content.

content delivery network

Cacheable landing pages are also a great solution if your page load times are slow.


HTTP requests are a significant component of your site’s response time, so reducing those requests should be one of your first concerns. Once your site has fewer items that need to be loaded (including scripts, images and style sheets), it will load faster. You can also speed up browser rendering by specifying a unique character set in HTTP headers.

Think about redirects. Since every redirect triggers an additional HTTP request, redirects add latency, so make sure to only keep those redirects that are technically required and cannot otherwise be solved. Google has a set of recommendations concerning redirects.

Bad Requests put an additional strain on your site and cause wasteful requests. Both 404 and 410 errors will cause elements not to load, so use a broken link checker and optimize your page.

CSS, JavaScript and Images

Optimize images. This issue is often overlooked despite the fact that it is essential to your site’s load time. Especially in the case of websites with multiple authors, you may be surprised to find enormous images. Use a WordPress plugin such as Smush.it or Imsanity to make sure that all images are scaled to the width and height that you specify. Browsers will start loading your page before the images start loading. It’s important to specify image dimensions if you don’t wish your browser to reflow after they’ve finished downloading.

Minify CSS. Many webmasters overlook CSS, but such files may comprise hundreds and even tens of thousands of lines of code. File sizes also increase with each character (including commas, line breaks, space and tab). Minifying CSS will ensure that all the unnecessary bits and characters are eliminated before being uploaded to your website.

minify css and site speed

Use CSS sprites to combine images. Instead of having multiple background images, Sprites combines them into one single image. Consequently, roundtrip-related delays, overhead requests and the total number bytes that a page downloads are reduced.

Avoid having stylesheets in the document head. Browsers will not allow rendering if your stylesheets are placed in the document’s head. So make sure that both them and JavaScript code is placed at the bottom of your page.

By now, you already know that speed matters. A lot. Fancy effects, large images and flashy JavaScript may look great but in the real world, they only act as a bandwidth hog. So be clever when designing your website so that you don’t compromise lightning-fast loading speed fir aesthetics. Feel free to let us know if we’ve missed any things that have helped you improve your site’s loading speed.

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