Image buttons must have alternate text
Rule Description
When an image is being used as an <input> button, it must have alternate text to allow screen reader users to know its purpose.
The Algorithm, in Simple Terms
Ensures that every <input type="image"> has an accessible name.
Why this is Important
An <input type="image"> button must have alternate text, otherwise screen reader users will not know the button's purpose. Even if the image contains only text, it still requires alternate text, since a screen reader cannot translate images of words into output.
Text Alone Is Not A Label: Just typing text next to the form element is not sufficient to create a true label. To ensure accuracy, assistive technologies like screen readers need labels that can be programmatically determined from the code. Some screen readers are programmed to guess what the label should be, based on the surrounding text, but this method is not fool-proof, and can lead to confusion if the screen reader guesses wrong.
How to Fix the Problem
Check that the <input type="image"> has a non-empty alt, aria-label or aria-labelledby attribute.
Image buttons use the alt attribute as the label. The alt attribute value must be provided, and it must be clear and concise and representative of the action performed when the button is activated by the user (not a description of the image itself).
Image Button Example
<input type="image" src="submit.png" name="submit"
height="36" width="113" alt="Submit">Check that all images being used as buttons have accessible alternate text.
How to add alt text to an image
- Using an
altattribute i.e.<input type="image" alt="submit button"> - Using an
aria-labeli.e.<input type="image" aria-label="submit button"> - Using an
aria-labelledbyattribute i.e.<input type="image" aria-labelledby="someElementID">
If you are using an alt attribute or an aria-label, ensure it is not empty. If you are using an aria-labelledby attribute, ensure that the ID to which it points exists and is accessible to a screen reader (i.e. is not hidden using CSS with display: none or aria-hidden="true").
Tips on writing alt text
When writing the alt text, keep in mind that the purpose of the alt text is to relay information to blind users about the image’s contents and purpose - blind users should be able to get as much information from alt text as a sighted user gets from the image itself. alt text should give the intent, purpose, and meaning of the image.
When writing alt text, it is helpful to keep the following questions in mind:
- Why is the non-text content here?
- What information is it presenting?
- What purpose does it fulfill?
- If I could not use the non-text content, what words would I use to convey the same information or function?
Be sure that all text contained in the alt attribute is useful. Words like "chart," "image," "diagram," or image file names tend not to be very useful and thus should not be used in alt text.
Additional Information
- HTML 4
- HTML5
- ARIA