Your daily frequent11y newsletter, brought to you by @ChrisBAshton:
Writing Alt Text for Data Visualization
- Amy Cesal guides us through the W3C guidelines for alt text for complex images. I actually learned a lot from this article:
- There’s a
longdescattribute for images, which can refer to other areas of the page. E.g.<img alt="Short description" longdesc="#desc" /><div id="desc">Long description goes here</div>. - Screen readers read alt text linearly, meaning they can’t go back a word if they missed something – so keep it short.
- Supplement with a link to the raw data, so curious readers can access the data in their preferred program. But don’t put the link in the alt text – it needs to be clickable.
- Alt text for charts should generally follow the pattern
[CHART TYPE] of [TYPE OF DATA] where [REASON FOR CHART]. For example, “Line graph of number of bananas sold per day in the last year where the winter months have more banana sales”. - Finally, Amy describes how to add alt text on popular platforms such as Twitter, Medium, Microsoft Office and Instagram (which I didn’t know supported alt!).
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