Site Speed

by SEOMoz

When Google made their “page speed is now a ranking factor” announcement, it wasn’t a significant new ranking factor, but it is significant because it means Google wants to use usability metrics to help rank pages. Your site speed should be a priority as slow sites decrease customer satisfaction and research has shown that an improvement in site speed can increase conversions.

To better understand how fast the web is (as of February 2011), I collected site speed data from approximately 100 different sites. This data allowed me to create a very close approximation of the equation that Google currently uses to report (in Webmaster Tools) how fast sites are relative to each other:

The x axis in this graph shows the page load time (in seconds) and the y axis represents the per cent of sites that the corresponding time is faster than. So if a page loads in 4.3 seconds, it is faster than 31% of other pages on the web.

  • If your site loads in 5 seconds it is faster than approximately 25% of the web
  • If your site loads in 2.9 seconds it is faster than approximately 50% of the web
  • If your site loads in 1.7 seconds it is faster than approximately 75% of the web
  • If your site loads in 0.8 seconds it is faster than approximately 94% of the web
  • Minimize HTTP Requests – Your pages will load faster if they have to wait for fewer HTTP requests. This means reducing the number of items that need to be loaded, such as scripts, style sheets, and images.
  • Combine all of your CSS into an external file and link to it from the head section each page instead of loading it in the HTML of a page. This allows the external page to be cached so that it loads faster. JavaScript should be handled in a similar fashion as CSS.
  • Use CSS sprites whenever possible – This combines images used in the background into one image and reduces the number of HTTP requests made.
  • Make sure your images are optimized for the web – If you have Photoshop, this can be done by simply clicking “save for web” instead of “save”. By optimizing the formats of the images you are essentially formatting the images in a smarter way so that you end up with a smaller file size. Smashing Magazine has a nice article on optimizing png images.
  • Use server side caching – This creates a html page for a URL so that dynamic sites don’t have to build a page each time that URL is requested.
  • Use Gzip – Gzip will significantly compress the size of the page sent to the browser which then uncompresses the information and displays it for the user. Many sites who use Gzip are able to reduce the file size by upwards of 70%. You can see if sites are using Gzip and how much the page has been compressed by using GID Zip Test.
  • Use a Content Delivery Network – Using a CDN allow your users to download information in parallel, helping your site to load faster. CDNs are becoming increasingly affordable with services like Amazon CloudFront.
  • Reduce 301 Redirects – Don’t use 301 redirects if possible; definitely don’t stack 301’s on top of each other. 301 redirects force the browser to a new URL and require the browser to wait for the HTTP request to come back.

If you want to do further research on improving your site speed, Google has a good list of helpful articles for optimizing your page speed here that are much more in-depth than the above suggestions. To get suggestions specific to your website, tools like YSLOW and the HTML suggestions in Google Webmaster Tools are great resources.