When creating accessible content for students with visual impairments or incorporating Universal Design for Learning (UDL) considerations for incorporating alternatives to visual content, a commonly discussed strategy is the use of text-based descriptions that describe key visual information for audiences that would not otherwise be able to see it. While a missing description can render an image or visual information invisible or inaccessible for assistive technology users, having descriptions that are not useful or meaningful can be just as frustrating for students with visual impairments that rely on them to access information. Here is a list of tips for writing meaningful and relevant alt text for educational content, from a student with low vision.
Terms and definitions for text-based descriptions
Text-based descriptions and media descriptions are used to provide nonvisual access to visual information, ensuring that audiences do not have to solely rely on vision to understand what is happening in an image or to identify what they need to know. This is especially important when making content accessible for visual impairment, which I use as an umbrella term inclusive of blind, low vision, and neurological visual impairment (also known as cortical visual impairment/cerebral visual impairment or CVI).
It’s important to remember that visual impairment is a spectrum, not a binary, and that there are many tools and strategies that individuals may use when accessing digital content— though writing alt text and image descriptions is a great strategy for improving both visual accessibility and non-visual accessibility. These descriptions can also be useful for supporting learners with other access needs that benefit from having text-based equivalents of visual content.
ALT TEXT (ALTERNATIVE TEXT)
Alt text refers to a short, text-based description of an image that is read by screen readers or displayed on a braille display in lieu of an image. If an image fails to load on a website, alt text will display in its place for all users. Alt text is generally not visible to people who do not use assistive technologies, with the exception of some social media platforms. Alt text can be embedded in images posted online, on social media, or in documents.
IMAGE DESCRIPTION
Image descriptions are text-based descriptions of an image that are displayed as part of captions or are “exposed” so that anyone can read them or benefit from them. They may also be read out loud with a screen reader or displayed on a braille display. Image descriptions are often longer and more detailed than alt text, and also provide options for formatting text with lists, additional spacing, and more. Image descriptions can also be viewed in large print.
In longer documents or for visually complex images, image descriptions may be hyperlinked or added as supplementary material that readers can access in a new tab or refer back to at a later time.
TEXT-TO-SPEECH
Text-to-speech and speech synthesis tools read text out loud or convert text content to braille, and enable people with visual impairments to access visual interfaces with gestures, keyboard shortcuts, or without having to look at the screen. Screen readers will recognize text, labeled buttons, emoji, keyboard input, menus, and images that have alt text included, and will display the alt text in lieu of the image. Images that do not have alt text are essentially invisible, and the user has no way of knowing what is in an image unless there is alt text included.
Some users will activate text-to-speech or screen readers as needed for short reading tasks and use them in addition to accessing information visually, though many users completely rely on a screen reader and/or connected braille display to access information.
TRANSCRIPT
One option for formatting image descriptions for content with a mix of text and non-text content or for videos is to use a transcript. This is the optimal format for writing text-based video descriptions or for visual content that incorporates a significant amount of both images and text, as it is ideal for non-visual access and can be especially useful for people with cerebral visual impairment/cortical visual impairment (CVI) who may find it difficult or impossible to access visually complex images.
Audio narrated images and audio description
Audio description is a secondary narrative audio track that describes visual information in audiovisual content for audiences who would not otherwise be able to see it. Narration is typically read during natural pauses in dialogue. Audio description strategies may also be used for still/static images, which may be referred to as audio narrated images. While this guide primarily focuses on the use of media descriptions for visual content and not audiovisual content, many of the recommended strategies still apply to creating audio description.
Related links
- How To Write Alt Text and Image Descriptions for the Visually Impaired
- How To Write Alt Text For Digital Comics
- How To Write Video Descriptions For Animal Videos
- Fast Facts About Audio Description
- Creating Audio Narrated Images For Low Vision
How to add alt text to educational materials
Since alt text cannot usually be reused if an image is inserted multiple times, I recommend writing alt text and image descriptions in a separate document and then copy/pasting them into the appropriate location. A text box for inserting alternative text (alt text) is typically listed under Image Options when inserting a new image or editing an existing one. It may also be flagged as part of an accessibility checker. Image descriptions can be inserted as a caption for the image or within body text so that it can be read by anyone regardless of if they are using assistive technology.
It is helpful to include both alt text and an image description for content, and both types of descriptions can be accessed with assistive technology. Alt text often has a character limit that may limit users to writing much shorter descriptions, so image descriptions can help “fill in the blanks” and provide more detailed information about what is in an image.
Related links
- Designing Accessible Documents With Microsoft Word
- Adapting Accessible Charts: Math Problems and Low Vision
- Secret Microsoft Office Accessibility Features I Use Every Day
If an image has alt text, is it accessible?
Not necessarily. The goal of alt text or media descriptions in general is to provide equivalent access to images and visual content. Automatically generated, generic, or vague descriptions often do not meet this goal when used in educational contexts, and there have been many times where I have encountered content that was technically accessible, but useless to me as the reader. For example, I once read through a document for an anatomy class that contained the following words and phrases embedded as alt text for several images:
- Graph
- Image
- Photo
- Heart
- Screenshot
- Text
- Math
- Diagram
- Chart
Imagine having to answer a question about an image, and this is the only information you have access to— it’s no surprise that a student with visual impairment would fail the chapter quiz! This is why learning to write meaningful alt text and image descriptions is so important, because these descriptions ensure that everyone has access to the same information.
Related links
- How To Describe Science Experiments For Visually Impaired Students
- How To Modify Accessible Anatomy Graphics For Low Vision
- How To Create Accessible Classroom Posters For Students With Visual Impairments
Identify the purpose of the image
Before writing a media description, identify the purpose of the image/video to begin with. Why is it being included? What detail(s) are users expected to notice? What information do they need from the image to answer a question? If an image is purely for decorative purposes, consider removing it entirely or indicate that it is decorative either by selecting the appropriate check box or writing “null” alt text.
When possible, choose high resolution images and videos that provide options for zooming in/magnification, as this can enhance visual accessibility and can be used with other assistive technologies.
Related links
Take a conversational approach to descriptions
Some automatically generated alt text will list items that appear in the image, similar to a list of tags for a blog post. Instead of identifying a list of keywords or characteristics of an image when writing alt text for educational content, it is more helpful to take a narrative approach and write descriptions as sentences.
When it comes to writing alt text and image descriptions, one helpful strategy is to imagine someone is on a phone call describing an image to a friend, and what details they would want their friend to know about in order to understand the image or following along in conversation. Others may find it more helpful to imagine they are describing an item on a podcast or radio show where the listener can’t ask clarifying questions.
Show, don’t tell
In educational contexts, it is critical that media descriptions are written so that they aren’t giving away the answer to a question or skipping problem solving steps. Some examples of how this can be implemented include:
- When writing alt text for questions like “what term matches this image?”, write the definition of the term as the image alt text instead of the term itself.
- For pictographs, share the key for symbols and then how many symbols are present in each column. For example, “one apple represents four kilograms. Fuji: 3 apples.”
- Write out any text in the image verbatim, including punctuation and symbols.
- On a coordinate plane, include information needed to solve the equations such as the vertex, points of interest, pattern/direction, etc.
- For graphs and charts, include a table or link to the data that is included in the visualization as an image description. For larger datasets, a CSV file can be used to provide users with a link to the data.
The level of detail required for an image will depend on the image’s purpose. For example, if the goal of an image is to teach someone what a flamingo looks like, the accompanying media description is going to be much more detailed than an image that is intended to highlight the environment where the flamingo lives.
Related links
- Adapting Coordinate Planes: Math Problems and Low Vision
- Taking Online History Classes With Low Vision
- How To Create Accessible Pie Charts For Low Vision
- Emoji Accessibility and Low Vision
Proofread media descriptions before sharing
A missing number or extra letter can make a significant difference when reading or accessing media descriptions, or lead to confusion about what information is being presented. Many alt text editors do not have a proofreading or editing function, so check the text in another application before adding it to the image. This is another reason why I recommend writing alt text and/or image descriptions in a separate document and copy/pasting descriptions as needed.
Related links
- Adapting Digital Equations: Math Problems and Low Vision
- Make Proofreading Feedback Accessible For Low Vision
A note on AI-generated alt text
There are a few different AI tools that can be used to generate alt text or media descriptions for content, though they cannot be used in educational contexts without careful editing to ensure that the generated description is relevant and that it is written with its intended purpose in mind. Some issues that may arise when using AI-generated alt text include:
- The description does not provide sufficient information needed to solve the problem. Information may be missing or incorrect.
- Too much information is provided in the description, which can include answers to questions or overly detailed descriptions that are too advanced/too basic.
- The resulting alt text is very generic or seems unsure of itself, e.g. “may be image of graph”
- Descriptions repeat information or contain errors
- The description is for a completely different image or includes hallucinations
AI tools can be a great starting point for creating media descriptions, but they must be edited and/or proofread before including them in educational materials. To be clear, I am not wholly against the use of AI-generated descriptions in all contexts— I frequently use them to extract text or to answer questions about an image that aren’t addressed in alt text, but I can’t rely on them during quizzes or tests. Most AI-generated descriptions are written with the goal of giving the user an answer or to solve a problem, not with the goal of giving the user the information they need to come up with an answer on their own.
Related links
- Purposes of Media Descriptions for Visual Impairment
- How To Access Images Without Alt Text
- Recognizing Images With Seeing AI
- Using The Envision App With Low Vision
- All About Visual Assistance Apps For Visually Impaired
- Ways To Use Visual Assistance Apps For Virtual Classes
More resources on how to write alt text for educational content
- Students may need to request specific disability accommodations to receive alt text and/or image descriptions for academic materials. Learn more about classroom accommodations in Common Classroom Accommodations For Low Vision
- Want to learn more about how I use alt text and image descriptions as someone who primarily accesses visual media like large print? Check out Purposes of Media Descriptions for Visual Impairment
- Interested in learning how to describe science and math content specifically? I have several posts on this topic in Science and Math category — Veroniiiica
Published March 7, 2025. Updated March 2025