Years ago, a colleague of mine had taken up scrapbooking, and her material of choice was the communal office newspaper. I’d pick it up on a break and find clean, careful cutouts where photos, charts, and figures used to be. The trouble was the text around those holes had been written assuming the graphic was still there. “as the chart above shows,” with a caption pointing at nothing, and a paragraph that only resolved if you could see what it was gesturing at. I’d read around the hole and come away having understood less than if the article had just been shorter.
I thought about that newspaper recently, reading a post on tempertemper, Martin Underhill’s accessibility blog. He makes a claim that stopped me: a chart image doesn’t always need to be exposed to a screen reader at all. What matters is that the information in it reaches the person some other way.
That’s not what I would have guessed. If you’ve spent any time around accessibility work, you’ve had “add alt text” drilled into you as the answer to basically everything visual. So my first reaction was to push back on it a little.
Then Underhill gives the example that talked me out of that reaction. Take a pie chart with ten or so slices — nothing exotic, just a normal chart you’d drop into a slide deck. Write proper alt text for it and you end up with a sentence like “22% chose the first option, 18% chose the second, 15% chose the third,” on and on through every slice. Technically, that’s compliant. Practically, it’s a wall of numbers read aloud with no way to skip ahead, no way to compare two values against each other, nothing to hold onto. You’ve solved the letter of the requirement and missed the point of it.
That’s the reframe: image accessibility and data accessibility are not the same problem. You can make a chart technically readable by a screen reader and still fail to get the actual information across. Writing a longer, more careful alt text doesn’t fix that — it just makes the wall of numbers longer.
Once that clicked, I kept thinking about where it actually shows up for us. Picture a lecture slide with a chart on it: enrollment trends, survey results, whatever. The instructor exports the deck to PDF and posts it to the course page. To them, it looks finished. There’s a chart, it’s got a title, it’s got labels. But if a student using a screen reader opens that PDF, there’s a real chance none of that data reaches them at all. The instructor has no way of knowing, because the thing that would tell them is invisible by definition.
It gets messier once you’re dealing with anything interactive — a stock chart with hover tooltips, a dashboard someone can filter and drill into. In my experience, the simplest and most reliable fix in most cases is still the same one: offer a static table of the same data as an alternative. It’s the version that’s easy to verify and doesn’t ask the user to discover anything. It just has to be there.
I went looking to see if this was just one person’s take, and it isn’t. Harvard Library’s accessible content guidelines land on the same fix, independently: if you’re including a chart or infographic, provide a text alternative or a link to the underlying data. Different source, different context, same conclusion — the fix isn’t a better description of the picture, it’s making sure the numbers themselves are reachable, whether that’s a simple table next to the chart or a link to where the data lives.
So the question I’m asking myself now when I look at a chart isn’t “does this have alt text.” It’s “if someone can’t see this, can they still get to the numbers.” Those turn out to be different questions, and only one of them actually matters.
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