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Re: - Reg: Screen reader testing when screen Resized or Reflow settings applied on the page.

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From: Steve Green
Date: Jan 24, 2025 7:46AM

Both approaches are wrong. The normative text includes "Vertical scrolling content at a width equivalent to 320 CSS pixels". The phrase "equivalent to 320 CSS pixels " is important because it does not say "equal to 320 CSS pixels". The second approach is wrong on this basis.

NOTE 1 says "320 CSS pixels is equivalent to a starting viewport width of 1280 CSS pixels wide at 400% zoom." This is not normative, but no alternatives are mentioned so you would have to have a very good reason to do anything different.

Furthermore, the Intent section of the Understanding page refers to scaling content to 400% and the page contains several other references to that zoom level. Again, the page is not normative, but you would have to have a very good reason to do anything different.

When testing content that scrolls vertically, the SC does not specify a browser window height. We have discussed this many times if you want to look at the archives. My view is that there must be no loss of information or functionality with a full height window on a 1920 x 1080px monitor because the vast majority of people will have that size or smaller.

Testing with smaller windows is more subjective. According to Statcounter, about 23% of users worldwide had screen resolutions of either 1366 x 788 or 1536 x 864 (split equally) in December 2024, so there is a strong argument for testing with window heights (including the browser chrome) as low as 788px.
https://gs.statcounter.com/screen-resolution-stats/desktop/worldwide

Steve Green
Managing Director
Test Partners Ltd