Authoring Meaningful Alternative Text

Creating Alternative Text

When writing alternative text, focus on context and why is this image here and what's the important part? If it appears in a document and an assessment, the alt text should be consistent, so students are recalling the same information. Avoid over-describing, as too much detail can cause cognitive overload. Get to the purpose and only provide a longer description if truly needed.  Ask yourself these guiding questions. 

1. Does this image add meaningful information to the content? 
2. If so, what is the overall message that the user needs to understand? 
   
   

For content like assessments, there needs to be a balance. Describe enough without giving away the answer. For example, describing a cell with a large central structure, a folded membrane system, and small dot-like structures scattered throughout conveys the image meaningfully without naming the organelles. Focus on what's intentionally important, like shape, structure, or location, and you can guide them without revealing the answer. 

Remember to use punctuation when creating alternative text. Punctuation tells assistive technology when to pause or stop, helping the description flow naturally when read aloud. For example, a period at the end of alt text signals a natural stopping point rather than running directly into the surrounding content.  

Building Context Beyond Description

An educational resource on European architecture features an image of Westminster Abbey with only the building's name as a label. The alt text provided reads "A building with English Gothic architectural style." While this describes the appearance it misses what makes Westminster Abbey significant to someone who may not already know what it is. 

A more meaningful alt text would be: "An Anglican church in the City of Westminster, serving as the traditional site of British royal coronations and burials. The building features English Gothic architecture with twin towers and ornate stone facades." 

Summarizing Data Meaningfully

This graph shows opening weekend box office earnings for Disney Renaissance films and has the alternative text "The Lion King had the highest opening weekend of the Disney Renaissance era with $40,900,000 domestically in 1994." This description simply provides the overall information that the reader needs. 

It is possible to go in depth and explain all the individual films and their individual opening weekends, but in this example the creator of this chart has chosen to provide only the main takeaway as the alternative text. 

Ultimately, the appropriate level of detail in alternative text is a judgment call that only the author can make. The author alone understands their content well enough to determine how much information the alternative text needs to convey.

Generating Alternative Text with Automated Tools

AI‑generated alt text can be a helpful starting point, but it often misses important context or intent and must be reviewed for accuracy. 

Consider the following image:

The AI generated alt text reads: "A 3D rendered illustration of a drinking fountain mounted on a beige wall between two wooden benches with metal supports on a tiled floor. The scene depicts a simple, clean public space designed for seating and hydration." This is a good starting point, but appropriate alternative text will always depend on where the image appears and what purpose it serves. 

This example appears in a guide referencing ABA Standards explaining that fixed objects such as benches and planters can be used to recess drinking fountains and keep them compliant as protruding objects. With that context a more appropriate alt text could be: "Drinking fountain recessed between two benches forming a section to limit protrusion into the walkway." 

A simpler description like "Drinking fountain on wall with benches on both sides" can also be appropriate, allowing the surrounding text to provide context while the alt text confirms what is shown. Both can be correct. The author is the only one who can determine which level of detail serves the reader best. 

This is why AI generated alt text should always be treated as a first draft. Review it against the surrounding content and ask yourself if this description tells the reader what they need to understand from this image in this specific context.

Marking Non-text Content as Decorative 

Images should be marked as decorative when they don't add information to the document's content. Key examples include:  

• Generic images/Stock photos – Images that are illustrative like a character with question marks surrounding them for a FAQ page or a photo of people sitting in a field that isn't directly relevant to the topic being discussed.
  • A generic image that would require alternative text would need to be used for evoking a feeling or setting up the environment for the user.
    
    
• Repeated logos – A company logo on a multi-page document. 
  • Alt text could be created for the logo on the first page
    
    
• Design elements – Background gradients, textures, divider lines, arrows, and decorative borders.  
  
  

If removing the image doesn’t take away from the information, mark it as decorative. However, if an image carries specific meaning, like a logo for a company, it should have alt text. 

Alternative Text Decision Tree 

1. Does the image add information that the text doesn't include? 
   1. If yes, add descriptive alternative text 
   2. If not, mark it as decorative 
2. Would a sighted reader learn something from seeing this image? 
   1. If yes, it's meaningful and should have alternative text. 
   2. If not, mark it as decorative. 
3. Would removing the image change the overall understanding? 
   1. If yes, it is not decorative and you should give it alternative text. 
   2. If not, mark it as decorative. 
      
      

For more complex scenarios visit the W3C Web Accessibility Initiative's resource on the topic: Image Concept Decision Tree.