Skip to main content

6 Bottles of RUM: Surprising Stories of Mobile Behavior in the Real World

Peter McLachlan (Mobify)
Mobile, The Leading Edge, User Interface & User Experience
Location: Salon 14 Level: Intermediate
Average rating: ****.
(4.00, 6 ratings)
Slides:   1-ZIP 

Thanks to browser abstraction, web developers enjoy a remarkably homogeneous development environment across wildly different computing architectures. But abstraction only provides the illusion of a common platform: the implementation complexities of browser, operating system, hardware and wireless networks can turn development best practices into anti-patterns.

Real world measurement at scale is the only reliable way for web engineers to understand the performance behaviour of routine techniques, considered to be best practices in desktop web development, on smartphones running on cellular data networks. Intimate knowledge of browser, phone and network behaviour is a “must” for creating engaging web experiences for mobile browsers.

In this talk, we’ll go over surprising results of real world RUM tests on modern mobile web browsers with millions of samples answering questions such as:

  • How long does it take the average phone to download content from a “cold” connection?
  • How big is the difference between a warm connection and a cold one?
  • Is it useful to use a cookie-free domain for serving static assets? How big a difference does it make?
  • Does DNS pre-fetching make a difference?
  • Is domain sharding a best practice for mobile?
  • When should you use data URIs?
  • Should you use CSS sprites on mobile?
  • Does CSS complexity significantly impact mobile rendering speed on modern smartphones?
Photo of Peter McLachlan

Peter McLachlan


Peter McLachlan is Chief Architect and Co-Founder at Mobify, a mobile development company based in Vancouver, Canada. Peter holds an MSc in Computer Science in data visualization with a specialization in Human Computer Interaction and has publications in data visualization and haptics in peer reviewed conferences. In a previous life he built HPC supercomputer clusters for feature animation and scientific computing as a team member at IBM. He writes about mobile web development on Mobify’s blog: