Alternative Text

Alternative text (often called alt text) is a short written description of an image that explains what the image shows or what purpose it serves.

It’s mainly used for:

• Accessibility — screen readers read alt text aloud for people who are blind or have low vision.
• When images don’t load — the text appears instead of the image.
• Context and searchability — helps software understand image content.

Examples:

• Image: office conference room with four people at a table
  Alt text: “Four people meeting around a table in an office setting.”

• Image: company logo
  Alt text: “UNT System logo.”

• Decorative image with no meaning.
  Alt text: Often left empty so screen readers skip it, if it is not important to the content.

Good alt text usually:

• Describes the important information in the image.
• Stays concise.
• Avoids phrases like “image of” or “picture of” unless relevant.

Why is alt text important?

Providing alt text makes images accessible to people who are blind.  Descriptive text of the image is read by a screenreader to the user who may not be able to see the image.  The alt text is also helpful if an image does not load (for example, if internet connection is slow).

Will everyone see the alt text?

Alt text is not typically visible in a document or webpage. It is available to people using a screen reader to allow them to access the content of an image.

How long should my alt text be?

Alt text should be a concise description, approximately 150 characters or 1 to 2 sentences. If a longer description is needed, that description should be provided in the main body of the document or in supplementary documentation instead of alt text.

For complex diagrams such as graphs and flowcharts, you should provide the steps on the page.  The alt text should be short, for example, “Flowchart of Procurement process; longer description to follow”. 

Review 

What if my image doesn't contain any meaningful or important content?

If you have an image that is purely meant for visual decoration and contains no meaningful content, you can mark the image as decorative instead of adding alt text.

The way to do this depends on your content editor. Most software will have a checkbox under image properties that is labeled "Mark image as decorative" or something similar. If the content editing software you're using does not have an option to mark images as decorative, then you should include a general description in the alt text field.

In HTML, you would add an empty, or null alt attribute (alt="") to the img element. Additionally, if an image contains meaningful content but all of the meaningful content is already provided elsewhere in the text of the document, then you can mark the image as decorative.

What is "good" alt text?

Writing alt text can be more of an art than a science. Ask yourself why the image is important in the context of the document, and let that guide your decisions on which details to include in the description.

It is best to put the most important information at the beginning of the alt text and avoid starting with phrases like "image of" or "photo of" as it is repetitive since screen reading software announces this information.

Lastly, avoid providing subjective interpretation. Just describe what is visually presented in a neutral tone.