Alt text
The alt text a checker cannot write
A rule can tell you an image has no alt attribute. It cannot tell you whether the alt should be empty, or should read like a sentence. That gap is the whole reason accessibility needs judgement.
Renata Cho, Head of Accessibility Research · July 15, 2026 · 6 minute read
Every free checker finds the same thing first: images with no alt attribute. It is the most common failure on the web, and it is the one people fix worst, because the fix a checker implies is wrong about half the time.
Three images, three correct answers
<img src="logo.svg">
<img src="divider.png">
<img src="q3-revenue.png">The logo should get a text alternative that names the company, because it carries meaning and it is probably a link to the home page. The divider is decoration and should get an empty alt, alt equals nothing, so a screen reader skips it entirely. The revenue chart needs a sentence: not its file name, not the word chart, but what it shows.
The fixes
<img src="logo.svg" alt="Northwind">
<img src="divider.png" alt="">
<img src="q3-revenue.png"
alt="Q3 revenue up 12 percent to $4.1M">Why a rule cannot make this call
To choose between those three, you have to understand what the image is doing on the page: is it decorative, is it a link, does it repeat text that is already there, or does it carry information the text does not. That is reading comprehension, not pattern matching. A rule can only see that the attribute is absent.
The failing grade is easy to compute. The passing grade is a paragraph of judgement.
Renata Cho
This is why Tallyn is built on language models rather than rules alone. It reads the paragraph next to the chart, notices the number in it, and drafts an alt that says what the chart shows. It tells the divider apart from the logo. When it is unsure whether an image is decorative, it says so, and it recommends empty alt only when the surrounding content already carries the meaning.
What to do this week
- Find every image with no alt attribute. That part a checker does well.
- For each, ask one question: if this image vanished, would the reader lose anything? If no, empty alt. If yes, write the sentence they would lose.
- Never let the file name be the answer. "q3-revenue.png" tells a screen reader user nothing.
- Re-check the page after you ship, so you know the decision landed.