What is Alternative Text?

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 (often called “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 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.

The following video clips demonstrate what images sound like to someone using a screen reader. The first is an example of an accessible image with alt text. The second shows what happens when alt text is not included.

Video: Alt Text with JAWS (Screen Reader)

Video: Screen Reader Reading Image without Alt Text

Writing Alt Text

Alternate text should be added to all non-text elements, including:

  • Pictures
  • Graphs
  • Charts
  • 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).

Adding Alt Text in Specific Software

Adding Alt Text in Acrobat

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

Adding Alt Text in Canvas

Canvas provides a text box for entering alternate text at the same time that you upload an image. In the text editor, click on the Images icon or use the Insert menu to upload an image.

Canvas - Insert Image Menu

At the bottom of the Upload Image window, type the image description in the Alt Text box, then submit the image.

Canvas Upload Image window with alt text entry box

Video: Adding Alt Text in Canvas

Adding Alt Text in Facebook

  • Add alternative text to any images that you post, including memes.
  • For memes with text in them, repeat the text but also include any context that helps the audience understand the point.
  • You can include the description in the text of the post, or edit the image to add it in the background.

To add alternative text, click or press on the photo to edit it:

Select edit photo after choosing the photo to upload

In the Edit Photo menu, press Alt text:

Alt text option in edit photo menu sidebar

Press "Override generated alt text" to add your description:

Click button to "Override generated alt text"

Coding Alternative Text in 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="">

Adding Alt Text in Instagram

To add alt text in Instagram, scroll down to Advanced Settings at the bottom before sharing a new post:

Advanced settings option on new Instagram post

In Advanced Settings, select Write Alt Text:

"Write alt text" under advanced settings in Instagram

In the new window, type a short description of the image in the text box. Select Done to return to the new post.

"Write alt text" text box in Instagram

*Note that alt text does not carry over automatically on posts shared from Instagram to Facebook. You'll need to edit alt text in Facebook after sharing.

Adding Alt Text in Office 365

Right-click on the image, then select Edit Alt Text from the menu.

Edit Alt Text option in context menu, Office 365

An alt text panel will open in the document pane to the right. Type a short description in the text box.

Text box with "Type short description here" in O365

If the image is decorative, you can check the Mark as Decorative checkbox instead. You should only use this option if no meaning will be lost to any audience who cannot see the image.

Check box to "mark as decorative" in O365

Adding Alternative Text in Office 2013 - 2016

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

Adding 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.

Adding Alt Text in 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