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Is ALT text necessary if there's an identical caption adjacent?

From: Francois Jordaan <Francois.Jordaan@wheel.co.uk>
Date: Fri, 30 Jul 2004 16:04:18 +0100
Message-ID: <1F53DAFF8879D248BA138A2E100BE7A7088173@VIRGO.intranet.wheel.co.uk>
To: w3c-wai-ig@w3.org

Recently the question cropped up at work whether ALT text is necessary on an
image if it is immediately adjacent to a caption with exactly the same text.
The following was my reply. What do other people think?

[I should mention the context in which this arose was in a shopping site,
when displaying a grid of product thumbnails images + captions.]

I believe ALT text that is identical to an adjacent caption is unnecessary,
and an irritant to screen reader users. I recommend alt="" in such cases.

There is no reason why ALT text would always be identical to a picture
caption, since the main purpose of the ALT text is to accurately describe
the image, while a caption can be much freer. BBC News articles are perfect
examples of this.

However, in the e-commerce world, pictures usually depict nothing besides
themselves, i.e. the product name. If the product name is immediately
adjacent in plain text, I think ALT text is unnecessary.

(Warning: this argument is weakened if the IMG and the caption are in
separate A tags. Because then a list of hyperlinks on the page (a
frequently-used feature in screen readers) will include many unidentified
links, which will be confusing. For the same reason, this argument also
requires the caption to be a hyperlink. If the caption isn't hyperlinked,
only the image, then the image should have ALT text even if it's the same as
the caption.)

Accessibility dilettantes (like most clients nowadays) have gotten used to
checking for ALT text by looking for tooltips. Thus the desirability of ALT
text has been conflated with a spurious desirability of tooltips for sighted
users. This is a dangerous generalisation that we should refute

In the absence of a visible caption, a tooltip can indeed be valuable to a
sighted user. Or a tooltip can be used to add useful additional information.
However, this should be facilitated by the TITLE attribute, as this is not
the intended use of the ALT attribute, nor do all browsers display ALT as a
tooltip. Under no circumstances should ALT text be used for anything besides
a literal description of the image. (Therefore no marketing messages.) If
this is done (ideally sparingly), TITLE should be used.


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