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:

  • Pictures
  • Graphs
  • Charts
  • Tables
  • Microsoft Office SmartArt

Make alternate text meaningful to a listener:

  1. What is the context of the image? What meaning does it add to the page?
  2. Be concise. Describe only what you expect visual users to get out of the image.
  3. If the image is already described in the surrounding text, the alt text can be very short.
  4. Avoid redundant statements like “Image of” or “This is a picture of.” Simply state what it is.
  5. If an image is purely decorative, mark it as such (various methods depending on software).

Use the Action Wizard in Acrobat to detect any images (Figures) in a PDF. (See instructions on using the accessibility checker in Acrobat.)

Acrobat DC - detect images in PDF

The Wizard will prompt you to add alternate text to any images it finds.

Acrobat DC - Add alt text to figure

Canvas provides a text box for entering alternate text at the same time that you upload an image.

Alt text field when inserting an image into Canvas

Alternate Text: Office 2013 & Later

Note: Sometimes images that are downloaded from the web have “junk” alternate text (usually a long file name). Make sure to manually check every image.

Right-click on the image, then select Format Picture from the menu. (This menu option may be Format Shape on other types of graphics).

Format picture is the last choice in the image context menu

A Format Picture menu will open in the document pane to the right. Select the Layout and Properties tab, the third option in the Format Picture Pane.

Format picture sidebar showing the layout & properties tab

If it is not expanded already, open the Alt Text menu by clicking on the arrow.

Type the alt text in the Description box. Ignore the Title field, since it will not be read by a screen reader.

Alt text description field

Alternate Text: Office 2010 & Earlier

Right-click on the image to get the "Format Picture" menu option.
Image context menu. Format Picture is the last option.

Click on the "Alt Text" menu on the bottom left.

The text goes in the "Description" section on the right (not the "Title" section).

Format picture menu. Alt text is the last item.

Alternate Text: WordPress

To add alternate text in WordPress, click on the image in the Media Library and edit the Alt Text field.

Alt Text field in WordPress media library

Alternate Text: HTML

When editing HTML code directly, include the alt attribute (“alternative text”) for all images. The alt attribute is added after the path to the file:

  • Example: <img src="file-name.jpg" alt="Descriptive text goes here.">

Alt text should describe the meaning of an image rather than its appearance. For example:

  • Poor: <img src=" lab_sign.gif" alt="Sign hanging on lab door.">
  • Better: <img src="lab_sign.gif" alt="Each laboratory has safety policies posted on the door.">

Purely decorative images (graphics that convey no information), require a “null” or “empty” alt attribute. The null attribute is a signal to screen reader software that the image is unimportant and can be skipped.

  • Example: <img src="spacer.gif" alt="">