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Ad BlockAd Speed
June 22, 2016

Study of 101 Websites Finds Ad Blocking Leads to 2X Improvement in Load Times

Users don't like slow websites. Studies have repeatedly found that as websites slow down, people visit fewer pages, buy fewer goods, and engage less often with content. But the backlash against slow

Chris Cummings

Users don't like slow websites. Studies have repeatedly found that as websites slow down, people visit fewer pages, buy fewer goods, and engage less often with content. But the backlash against slow websites may be more existential for sites that run advertising. A recent survey of more than 1,000 Internet users found that one of the primary reasons people use ad blockers is to speed up websites, suggesting that slow ads may now be contributing to the undoing of the advertising ecosystem altogether.

In this study, we decided to quantify the performance improvements provided by ad blockers. Users perceive ads to be slowing down websites, but how much impact do ads really have? To find out, we conducted an in-depth analysis of 101 of the most highly trafficked advertising-based sites on the Internet. We loaded each website ten times--five times with adblock and five times without--for a total of data set of 1,000 website load times. We then analyzed at the median load times, network requests, and download size for each website.

Here are the highlights from our findings:

  • Adblock caused websites to load an average of 113% faster, reducing average load times from 7.7 seconds to 3.6 seconds.
  • Adblock saved users an average of 56% on bandwidth by eliminating an average of 164 network requests per page; Adblock delivered a more consistent user experience, reducing the standard deviation for load times from 1.4 to 0.4.
  • Some websites distinguished themselves for their ability to effectively manage the impact of ads on load time, keeping the impact on site speed to 20% or less.

Anecdotally, while conducting the research, we ran across sites that never completed loading, delivered janky scrolling, allowed page content jump around while ads loaded, and crashed the browser. These negative user experience events virtually never happened with adblock active.

In the full report, we include specific data on the 100 sites we measured, details on the methodology, and examples of sites that have successfully limited the impact of ads on load times.

The full report.

If you have any questions or comments about the study, feel free to post them in the comments below.

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