Web performance impacts every metric that businesses care about

Anna Starasts

September 23, 2015

At this year’s FITC Web Unleashed, Tammy Everts of San Francisco-based performance consultancy SOASTA spoke about web performance to a captive audience of developers. There’s no wonder the room was packed. Everts is a compelling speaker and doesn’t mince words when explaining why developers should care about web performance: it impacts every metric that businesses care about.

Here’s are some key points from her talk, or else check out Tammy’s slides on SlideShare.

How does every 1 second of improved web performance impact your business?

1. Improved load times are correlated with an increase in your website’s conversion rate.

  • For your company this might mean sales leads, downloading thought leadership, or signing up for a newsletter.
  • What does this mean in practice? An example: Mozilla found that a 2.2% decrease in load time resulted in a 15.4% increase in downloads, totaling 10 million additional downloads annually.

2. When it comes to UX slow time is worse than down time. 

  •  Though it might seem worse, down time doesn’t have the same negative impact as slow load time.
  • The psychology of slow load times is clear in survey data, which show that users will go to a competitors site, never return to the site, and share their bad experience with others if they’re dissatisfied about slow load times.

What can you do to improve load time?

A) Focus on SIZE

  • Did you know pages have ballooned from 14.1KB in 1995 to 2099 KB in 2015?
  • 80-90% of response time is at the frontend, so opportunities to improve lie there. Know where your page weight is coming from.
  • Optimize your images: reformat or compress them, use adaptive images, auto-preload images based on predictive analytics of where your users will go next, or defer loading (load images lower on page after top images have been loaded).


  •  Third party content can be a big drag for speed, making up <50% of your page requests.
  • Some solutions: defer scripts if possible, monitor and be aware of the performance penalties associated with the content, and use asynchronous versions whenever possible.

Everts’ suggested reads on web performance:

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