Accessibility finding
The image contains text that the alternative text does not give
Accessibility Error Severity: High
Part of the audit Alternative text checked against the image itself. Finding id: accessibility.altMissesTextInImage.
What it costs you
If the alt leaves the words out, screen reader users hear that there is a picture and miss what it says.
What to do
Compare the alt with the text in the image. If information is missing, add it to the alt, or better, publish it as real text next to the image.
What it checks
- Image of text without description
- Description leaves out text in image
How to fix it
Give the text as text
- If the image is a banner or an infographic, write its words in the page as text and keep the image as illustration with a short alt.
- If that is not possible, put all the words of the image into the alt attribute.
How to check: Run this rule again.
A real case
Blind customers sued Target in 2006 because its website could not be used with a screen reader; among other barriers, images had no alternative text. Target settled in 2008 with a 6 million dollar fund for claimants and agreed to fix the site.
Thresholds
| Name | Default | Meaning |
|---|---|---|
min_words | 3 | Ignore images with fewer readable words than this (logos, single labels). |
min_ocr_confidence | 0.8 | Ignore text the OCR engine is less sure of than this. |
min_similarity | 0.5 | Share of words the alt must have in common with the text in the image, from 0 to 1. |
How to verify by hand
A person: compare the text read from the image with the alt. Decorative lettering and text repeated next to the image are the exceptions.
What this relies on
Text that is part of an image carries information, so the alternative has to give it.