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The Importance Of Site Speed For SEO

By far the biggest reason to improve the speed of your website is because visitors prefer fast loading sites. To the extent that your role involves caring about actual conversions rather than just number of visitors to the site, you should pay fanatical attention to the time it takes to download and render pages on your site.

Importance of Site Speed for SEO

There are three additional factors to consider from an SEO perspective:

  • Site speed is a direct (albeit small) ranking factor in Google – i.e. all else being equal, a faster site should rank better than a slower one – this is measured using toolbar data so as to avoid skewing towards sites hosted near the Mountain View, CA data centers used by googlebot.
  • The same factors that make people more likely to convert on fast sites make them more likely to visit more pages, consume more content and share / link to that content.
  • On large sites, the number of pages indexed (or the freshness of the indexed pages) is often limited by the number of pages googlebot can crawl. The faster your site responds, the greater the number of pages that are likely to get indexed.

How To Measure Page Speed

From a technical perspective, there are three important elements to page speed. In order of increasing time:

  • Time To First Byte: This is the amount of time it takes the server to respond to a request. It is the easiest to measure, but the least relevant to users or googlebot. You can measure and track this using the free account at pingdom.
  • Total Download Time: This includes the initial response time and is the amount of time it takes to download the full page (with or without external assets like images, JavaScript etc.). It is still largely about your server performance and is the most relevant metric for googlebot. You can analyze the factors contributing to this using tools like YSlow.
  • Total Time To Render: This includes both of the above, but also includes downloading all assets and rendering them in the browser. Complex JavaScript and any form of asynchronous features (e.g. AJAX) can delay this. This is the hardest to measure as it is so dependent on the users’ computers and browsers, but is also the most relevant for them as it is the factor which is most closely tied to user experience. The easiest way of analyzing this for most webmasters is to use Google Analytics which now tracks page load speed by default.

Getting Buy In For Fixing Site Speed

One of the most powerful sets of tools that an SEO practitioner can have in their toolkit is a set of tools for convincing clients and/or bosses that something is important and should be a priority fix.

If you find that your page load speed needs improvement but are struggling to get buy-in, these following arguments and tools can be convincing:

Video Demonstrations

By comparing your page loading side by side with competitors and high profile (fast!) sites you can often create convincing arguments. The video comparison tool from webpagetest is fantastic for creating compelling boss-friendly videos.

Site Speed Video


Large sites have done extensive studies into the importance of page load speed to their conversions and revenue. Two great resources are Walmart’s analysis and data from High Scalability:

  • “Amazon found every 100ms of latency cost them 1% in sales”
  • “Google found an extra .5 seconds in search page generation time dropped traffic by 20%”

What To Do About It

It is relatively unlikely on anything but the smallest sites that it will be your job to improve site speed directly. More likely it will sit between developers and systems administrators.

In brief, though, the three biggest likely culprits are:

  • Slow “time to first byte” or slow download speeds for static assets – most likely solved with server upgrades, additional caching or content delivery networks
  • Slow dynamic pages – most likely solved with improvements to the code or more aggressive caching
  • Slow full download or rendering – caused either by complex or asynchronous web pages or by loading many external resources – most likely solved with improvements to front-end code or consolidation of external services

It can be useful to use tools such as pagespeed from Google to diagnose the weakest links in your site’s speed.


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