Alternative text of images should not be repeated as text

Don't put the same text in the alt attribute value for a button or link in the text adjacent to the corresponding image or link.

Bad Example:

For example, given the icon markup <img alt="Home Page"/>, the adjacent text also says "Home Page". In such a scenario, a screen reader will announce this content to the user as "Home Page Home Page". The redundancy is unnecessary and potentially confusing:

Home Page

<p><a href="index.html"><img src="images/home-icon.png" alt="Home Page" width="24" height="25">Home Page</a></p>

In this scenario, the icon image's alt attribute value is better left empty by setting alt="".

Image buttons use the alt attribute as a label. The alt attribute value must be provided, and the value must be clear, concise, and representative of the action performed when the button is activated by the user and not a description of the button image itself.

Image Button Example

<input type="image" src="submit.png" name="submit" height="36" width="113" alt="Submit">

Alternative text writing tips

Keep in mind that the purpose of a button's alternative text is to relay information to blind users about the image’s contents and purpose. Blind users should receive equivalent information from an image's alternative text as a sighted user receives from the image. Alternative text should state the intent, purpose, and meaning of the image.

Keep the following questions in mind when writing alternative text for button images:

• What information does the button present?
• What purpose does the button fulfill?
• If I couldn't use an image as a button, what words would I use to convey button information or function?

Be sure that all text contained in the alt attribute is useful. Words like "chart," "image," "diagram," or image file names are not very useful.