Accessibility in a Test-Driven Development Environment

Bios & Handouts

Scheduled at 3:30pm in WB IV on Thursday January, 1.



  • Stefan Heymanns, Senior Software Engineer, Netflix Inc.

Session Details

  • Length of Session: 1-hr
  • Format: Lecture
  • Expertise Level: Beginner
  • Type of session: General Conference


At Netflix, all new UI features and changes to existing UI elements undergo rigorous A/B testing to measure their impact on the end user. This includes all non-trivial accessibility components. This presentation will investigate some of our (sometimes surprising) findings.


Netflix is one of the leaders in Big Data analytics and almost all new development is rigorously A/B tested before being productized. While experience, intuition, industry best practices and user studies provide valuable starting points, at-scale user testing often exposes surprising impact of even the smallest changes.

This presentation will investigate how small, innocuous changes to the UI can have surprising consequences, and how non-trivial accessibility improvements can affect the experience and behavior of the general user base as a whole.


  1. Introduction to A/B Testing at Netflix
  2. Exposing Unexpected Impact of UI Changes through A/B Testing
  3. Understanding the Overall User Impact by Introducing Accessibility Improvements

Disability Areas

Cognitive/Learning, Deaf/Hard of Hearing, Mobility, Vision

Topic Areas

Information Technology, Uncategorized, Web/Media Access

Speaker Bio(s)

Stefan Heymanns

Professional * Netflix Inc., Los Gatos, CA -- Senior UI Engineer (Web Player) (Oct. 2013 – Present)

* Stanford University, Stanford, CA -- Senior Front End Web Developer (SAA) (March 2010 – Oct. 2013)

* Yahoo! Inc., Sunnyvale, CA -- Front End Web Developer (Yahoo! Finance) (May 2009 – March 2010) -- Front End Web Developer (My Yahoo!) (Jan. 2008 – April 2009) -- “Juku” Front End Training Program (Oct. 2007 – Dec. 2007)

* Symantec Corp, Cupertino, CA -- Lead Web Developer (Aug. 2005 – Oct. 2007)

Education * San Francisco State University (Cum Laude 2006) -- BS Computer Science / Mathematics Minor