Images convey information quickly and powerfully—assuming they can been seen and understood. However, some readers may not understand the meaning of the image; others may not be able to see it due to visual impairment, personal viewing preferences (especially on the web), or technological limitations.
Alternate text (“alt text” or "alt tag") is added to an image to provide a textual alternative to visual information. Why is this important? Remember, some users won’t see your information; instead, they’ll hear it using text-to-speech or screen-reading software. By adding an alt text to an image, you make its meaning available to people who, for whatever reason, cannot see it.
Alternate text should be added to all non-text elements, including:
- Microsoft Office SmartArt
Make alternate text meaningful to a listener:
- What is the context of the image? What meaning does it add to the page?
- Be concise. Describe only what you expect visual users to get out of the image.
- If the image is already described in the surrounding text, the alt text can be very short.
- Avoid redundant statements like “Image of” or “This is a picture of.” Simply state what it is.
- If an image is purely decorative, mark it as such (various methods depending on software).