Alternative text is required for every non-decorative static image included in any digital file.  The purpose of alternative text is to provide concise descriptions that explain the purpose of the inclusion of the image in context for instructional purposes.  

This tutorial is on strategies for writing alt-text.  Refer to our Guide on Entering Alt-Text as needed.

Technological Reason: Not all images render on all devices and it is impossible to know in advance which students will not be able to see them.  Alt-Text allows a student who can not see an image to know what the image is and when possible what content it portrays.  This is more common than you might suspect.

Physical Reason: A student has low or no vision and due to a physical trait  and can never perceive the image even if properly rendered technologically.

A decorative image is one that has no instructional purpose.  They include

• Images of text that is already repeated nearby  (Ex: Figure 1 is listed in text below an image that also says Figure 1).
• Stylistic borders, dividers, and spacers
• Icons next to text labels
• Images that are purely "eye candy" or serve to add a visual element to a slide, but does not enhance the instructional content.

In this slide the picture of the human brain conveys no additional information than the text.  So it could be marked as a decorative image.

The image of the student working at a computer is decorative as it does not enhance the concept of FERPA nor is it related to the instructional material included in the document.  The ZOOM image, however should have the Alt-Text ZOOM as it describes the focus of the document.

Assume the slide indicates:

Giant pandas differ from red pandas.  They are not closely related, though they both have a fondness for bamboo.

Appropriate Alt-Text: A giant panda has black and white fur, a round face, and a stocky body as it eats a bamboo stalk. A red panda has red-brown fur, a pointed snout, a fluffy tail, and is much smaller with a slender build.

This image shows the break between different sizes of grains.  Alternative text must provide a substitute for the missing image based on instructional purposes.

Assume the Slides this image is located on says this in text:

• Silt/Class smaller than .063 mm
• Sand .063 mm to 2 mm
• Granule/Pebble > 2 mm

What should the alt-text be?

It depends on if you want students to know all the breakdowns shown in the graphic or if the graphic is only to support the written text.

If the student needs to know the breakdown of all 8 categories in this image, alt-text is used to briefly describe the image AND a datatable with the information conveyed in the image is added to the slide or a subsequent slide.

For Example: Chart showing grain size classifications from pebbles to silt/clay with corresponding particle size ranges and textures.

However, a data chart should also be included on the slide or subsequent slide in text indicating the breakdowns for each section.

A Long Description is necessary if the information in the graphic can not be captured in 1 to 2 sentences - roughly 250 characters.  In this situation IF the student needs to be able to identify the different grain sizes for all categories a second slide would be necessary that looks as the table below.

Alt-text should be limited to roughly no more than 256 characters or 1 to 2 sentences.  If an image can not be summed up in that amount of text a long description is required. The diagram above is too complex to capture in alt-text so a long description becomes necessary.

Alt-Text: A supply and demand curve showing quantity of gasoline in millions so gallons with an equilibrium price of $1.40.  Other equilibrium points are shown.  See long description for more details.

Long Description: (On another slide or page).

This diagram is a supply and demand graph showing the gasoline market.

• Axes:
  • The vertical axis represents price in dollars per gallon, ranging from $0.60 to $2.20.
  • The horizontal axis represents quantity of gasoline in millions of gallons, ranging from 300 to 900.
• Curves:
  • The supply curve (S) slopes upward.
  • The demand curve (D) slopes downward.
  • They intersect at point E, the equilibrium.
• Equilibrium:
  • Price: $1.40 per gallon.
  • Quantity: 600 million gallons.
• Above equilibrium:
  • At a price of $1.80 per gallon, supply is greater than demand.
  • This creates excess supply or surplus.
• Below equilibrium:
  • At a price of $1.20 per gallon, demand is greater than supply.
  • This creates excess demand or shortage.
• Labels on the graph mark:
  • “An above-equilibrium price” near surplus.
  • “A below-equilibrium price” near shortage.