Wendy Chisholm

Stairs make the building inaccessible, not the wheelchair. Co-author of Universal Design for Web Applications. Strategist for Microsoft. @wendyabc at twitter.

Archive for June, 2017

Screen size, resolution and zoom. Oh my.

with 5 comments

A few weeks ago I tweeted:

I received a bunch of great responses. Thank you.  Since people were using different screen resolutions and zoom levels, we took the resolution and zoom and turned it into an effective pixel (effective pixel is defined in this article about screen sizes and break points for responsive design). We found that the effective pixels from our respondents was about 850×500 effective pixels which is really close to a typical “phablet” resolution of 960×540 or 1024×640 in effective pixels.

In addition, we started collecting telemetry. The following chart shows the percentage of users on the y axis and the x axis is screen width: from 1000 through 2500 increasing by 100 (for 16 data points). Each screen width has two bars one indicating 100% zoom, the other indicating 300% or greater zoom. Note that all 16 data points have at least 1% for 100% zoom. 13 of the 16 have at least 1% for 300%+ zoom. Note that the 1900 screen width has the highest percentage of users for both 100% and >300%. It’s about 70% for 300%+ and ~40% for 100% zoom.

Chart showing percentage of users who use 100% zoom vs 300% or greater for 16 screen widths

It’s interesting data and this is just an initial insight. It’s great to have data that indicates people are using zoom at higher percentages than we anticipated.

We’re still debating what this means for us. However, it’s clear that the way we had been testing for WCAG 2.0 1.4.4 Resize Text was not sufficiently catching all of the issues our customers have been experiencing.


Written by wendy

June 19th, 2017 at 2:24 pm

Posted in musings