Alternative text for informational graphics

Overview

Obviously, blind users cannot see images. They rely on the ALT attribute associated with an image in order to understand the image's visual content.

Images that convey information should have an ALT value that accurately describes the image's key informational content, within the context of the page.

In this test we want to find out:

  • Do ALT texts accurately describe informational images?
    • Does the ALT text succintly provide the same informational content as the image?
    • If the image is a link or provides some other function when clicked, is that function clear from the ALT text? Examples: "Submit," "Register for session," etc.
    • Is the ALT text redundant? For example, a chart would merit empty ALT value ("") if that chart is immediately followed by an on-page full description of the chart's data.
    • Is the ALT text appropriate with respect to the surrounding text/images? For example, a stock image of a pit bull in a story about rescued dogs should get different ALT text than the same image used in a story about attack dogs.
    • Is the ALT text for an image within a link appropriately descriptive. For example, in a link to download a PDF, the web designer used a PDF icon to indicate the file type. The ALT for the PDF might read "PDF file."

Strengths

Thorough examination

Weakness

Manual and time consuming

Step 1: To be added later

Procedure

Rules Evaluated with this Technique

Rules evaluated with Keyboard Testing of Basic Links, Forms and Scripting
Test
Type
Description
Manual

Every img element must have alt attribute.

Manual

Descriptions should be meaningful and contain at least 7 and less than 90 characters.

Manual

The alt attribute content should not include file name of the image.

Manual

The alt attribute content should not include information that is redundant with the img element.