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Re: Testing SC 1.4.12 in multiple browsers


From: glen walker
Date: Sep 23, 2021 9:05AM

In theory, your application should work in every browser (firefox, safari,
chrome, edge, ie, opera) on every platform (mac, pc, mobile) with every
assistive technology (nvda, jaws, narrator, dragon, switch, talkback) at
every CSS breakpoint.

With unlimited budget and time, you could test every combination. But for
practical reasons, the testing is usually "limited" to a few combinations
(or even one combination in extreme cases). I say "limited" but that's
with respect to the various combinations. It's not limited in how
extensive the testing is regarding testing every element on the page.

More often than not, an accessibility issue that occurs with one
combination will also appear in a different combination. An image missing
alt text is going to be a problem no matter what browser you're testing
on. A list that is not semantic will be a problem no matter what browser
you're testing on. A table without headers is going to be a problem no
matter what browser you're testing on.

There are, of course, minor differences between the various combinations so
sometimes you can find a problem with one that doesn't exist on another.
For example, having something like "first name <input>" will show up as a
problem when testing with NVDA on both chrome and firefox but if you test
with JAWS, it reads ok on chrome (but not firefox). So if you were only
testing JAWS on chrome, you might miss the problem. (This is why I usually
look at the code too and not rely solely on a screen reader to find
issues. Even if a form reads ok, I typically look at the html to see if
the label is really associated with the field.)

Another difference between browsers is if you have a scrollable container
(overflow). When a container has a scrollbar, firefox makes that container
a tab stop but chrome does not. So now you have a tab stop that
potentially does not have a name or role. It could be confusing for a
screen reader user on firefox.

I know this is all digressing a bit from your original question, asking if
you needed to test 1.4.12 in all browsers. The short answer is "yes" -
test everywhere, or at least as much as possible.

In your particular case, I have not seen a problem with the Stylus plugin
*not* applying to iframes. I *do* see the problem with the bookmarklet not
applying to iframes. So Stylus should work if you want to test for
1.4.12. I edited my style and added the same code that the bookmarklet

* {
line-height: 1.5 !important;
letter-spacing: 0.12em !important;
word-spacing: 0.16em !important;
p{ margin-bottom: 2em !important;}

When I viewed a page with an <iframe>, the styles were applied to the
iframe. You can test it with
It has 2 nested iframes.