How Do I Use Google Gemini to Generate Alternative Text for Images?

Alternative text, or alt text, provides a written description of an image for individuals who are blind or visually impaired and use screen readers. When a screen reader encounters an image, it reads the alt text aloud so you can understand the image's content and purpose.

Google Gemini can help you draft alternative text for images. While it can significantly reduce the time needed to create alt text, you should review and edit all AI-generated descriptions for accuracy before publishing them.

How to Generate Alt Text Using Google Gemini

  1. Open Google Gemini and sign in with your University Google account.
  2. Click Upload Files in the prompt box.
    Google Gemini prompt box with Upload Files selected.
  3. Upload the image that needs alternative text.
  4. Enter the following prompt:

Create accurate alternative text for this image using fewer than 125 characters. Focus on the image’s purpose and do not begin with "image of" or "picture of."


Note. Image of the text above entered into the Gemini prompt box. 

  1. Submit the prompt.
  2. Review Gemini's response to ensure it accurately describes the image and its purpose within the surrounding content.
  3. Revise the description as needed before adding it to the image's alt text field.

Provide Context When Needed

The same image may require different alt text depending on how it is used. Providing Gemini with information about the image's purpose can help it generate a more relevant description.

For example:

This image appears in a lesson about public health prevention. Create accurate alternative text using fewer than 125 characters. Focus on the information learners need to understand.

Or:

Create alternative text using fewer than 125 characters. Focus on the relationship between the host, agent, and environment.

Providing context helps Gemini emphasize the information that is most important rather than describing every visible detail.

Review Gemini's Suggested Alt Text

Before using Gemini's response, confirm that the alt text follows these best practices:

  • Be concise: Keep the description to 125 characters or fewer.
  • Be accurate: Confirm that Gemini correctly identified the important people, objects, actions, labels, or information.
  • Focus on purpose: Describe what the image contributes to the surrounding content.
  • Consider context: Include the details learners need based on how the image is being used.
  • Avoid unnecessary phrases: Do not begin with "image of," "picture of," or similar wording.
  • Avoid redundancy: Do not repeat information already provided in nearby text or captions.
  • Do not use the file name: A file name such as chart-final.png does not provide a meaningful description.
  • Review all AI-generated content: Gemini may overlook details, misread text, or interpret an image incorrectly.

Complex Images

Alternative text should provide a concise description of an image and generally be no more than 125 characters. Some images, however, contain too much information to describe effectively within that limit. Examples include:

  • Charts and graphs
  • Infographics
  • Maps
  • Flowcharts
  • Scientific diagrams
  • Images containing important text

For these images, use Google Gemini to create concise alt text, then follow the University's instructions for creating a long description.

For guidance on creating and inserting long descriptions, see How do I insert a long description for an image?

Decorative Images

If an image is used only for visual decoration and does not communicate meaningful information, mark it as decorative rather than assigning it alternative text.

Examples of decorative images include:

  • Divider lines
  • Decorative borders
  • Background patterns
  • Design elements that do not provide information
  • Stock images that do not contribute to the meaning of the content

Do not mark an image as decorative if it communicates information learners need to understand.

Important Privacy Reminder

NOTE: Do not upload images containing confidential, protected, personally identifiable, or sensitive information to Google Gemini unless their use has been approved by the University.

Examples include:

  • Student records
  • Grades or identification numbers
  • Medical or disability information
  • Private communications
  • Confidential institutional information
  • Photographs of individuals who have not consented to their use

Gemini is a helpful tool for drafting alternative text, but you remain responsible for ensuring that the final description is accurate, appropriate, accessible, and protects sensitive information.

Need Additional Help?

For more on Google Gemini, visit Google Gemini.

If you have questions or need further assistance, Submit a Help Ticket to OneIT at https://services.help.charlotte.edu

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