Alt Text for Complex Images in Education: STOP Describing EVERYTHING!

During my years as an instructional designer in higher education, I’ve watched countless faculty members struggle with the same challenge: how to make their complex visual materials accessible without losing their minds or their entire prep week. I’ve sat in offices with STEM professors near tears, staring at PowerPoint slides filled with intricate diagrams, convinced that writing alt text for everything would take longer than creating the entire course!

I’m here to tell you it doesn’t have to be that way. After helping hundreds of educators navigate this challenge, I discovered a fundamental principle that changed everything: alt text should provide the same quick understanding that a sighted person gets from glancing at an image—no more, no less. If your sighted students need to examine an image closely to extract detailed information, then ALL your students deserve that information in an accessible format, not buried in overly long alt text.

This revelation transformed my approach and made the impossible suddenly manageable. Let me share what I’ve learned about making this process both efficient and equitable.

The Glance Test: A Game-Changing Principle

The biggest mistake sighted people make with writing alt text is that they think they have to describe everything—the good news, you don’t. So, you can breathe a sigh of relief!

It took me working with people who have low vision to realize everyone wants the same thing: “Tell me what I need to know!”

Here’s the breakthrough that revolutionized my instructional design practice: alt text should convey what someone understands in a 3-5 second glance at an image. That’s it. Not every data point, not every visual detail—just the purpose and main message.

What does everyone need to know at a glance?

Think about how sighted people actually interact with complex images in your materials. When you show a graph, students don’t instantly memorize every data point. They see “an upward trend” or “a comparison between groups.” That’s what your alt text should convey. The specific numbers? Those should be available to everyone in a more accessible format.

This principle accomplishes two critical goals:

1. It makes alt text manageable to write (because you’re not describing every pixel)
2. It promotes universal design by encouraging you to provide detailed data in formats that benefit everyone

Every image description, regardless of complexity, must convey the image’s context and purpose within your lesson. If you can’t articulate why an image is there and what students should understand from it, the image probably shouldn’t be in your materials.

Universal Design: When Everyone Benefits from Accessibility

The most powerful shift in my practice came when I stopped thinking of alternative formats as “accommodations” and started seeing them as good pedagogy for everyone. If an image is so complex that it requires close examination, why should only screen reader users get a clear, organized text version of that information?

Here’s what I now do for every complex image:

The Image: Shows the visual representation.

The Alt Text: Provides the “glance equivalent”—what the image is and its main message.

The Universal Resource: Detailed information available to ALL students

This approach has unexpected benefits I’ve witnessed repeatedly:

• International students can translate data tables more easily than complex visualizations
• Students with learning disabilities can process information at their own pace
• All students can copy data for their notes or further analysis
• Everyone can search text-based resources when studying

I once worked with an economics professor who resisted providing Excel files of his graph data, saying, “Students should learn to read graphs.” When he finally made the data available to everyone, he was amazed: students started creating their own visualizations, running additional analyses, and engaging with the material more deeply. The accessibility requirement forced him into a better teaching practice.

What Really Counts as Decorative? Context Is Everything

In my years of reviewing course materials, I’ve learned that truly decorative images are rare in educational settings. Let me be absolutely clear about what I’ve discovered through sometimes painful experience:

Truly decorative images are images that convey NO information and serve NO pedagogical purpose. If removed entirely, no one would notice or care. These include:

• Horizontal lines used purely as separators
• Abstract patterns used as slide backgrounds
• Generic borders or frames
• Colored boxes used only for visual appeal

These are NEVER decorative:

• Any image you reference in your lecture (“As you can see in this diagram…”)
• Any image that illustrates a concept, even if you think it’s “obvious”
• Images that set a mood or tone (Picture of George Washington on a page talking about presidents)
• Any data visualization, no matter how simple
• Images you find “too difficult” to describe (these especially need alternative formats)

Here’s my test: Would you be comfortable deleting this image entirely – so no one can see it? If not, it’s not decorative—it has purpose and context that must be conveyed.

The Alt Text Ecosystem: Every Element Has a Role

Through years of practice, I’ve developed a systematic approach where each element serves a specific function:

Alt Text: The Quick Glance (Under 200 Characters)

Provides the same immediate understanding a sighted person gets from a quick look. Identifies the image’s purpose or message.

Captions: Context for Everyone

Visible to all, captions add context, sources, or interpretive notes without describing what people can see. Never duplicate alt text in captions—they serve different purposes.

Surrounding Text: The Teaching Context

Text before the image sets up what students should notice. The text after the image explains the significance. This is where you teach, not in the alt text itself.

Alternative Formats: Detailed Information for Deep Engagement

When images require close examination, provide the detailed information in accessible formats for everyone:

• Data tables as downloadable spreadsheets
• Complex diagrams as structured text outlines
• Detailed maps as searchable text documents
• Mathematical proofs as step-by-step text explanations

Real Examples: The Glance Principle in Action

Let me share actual examples from courses I’ve helped develop, showing how this principle works:

Example 1: Climate Science – Complex Data Visualization

What a glance shows: There’s an upward trend over time. Alt text (152 characters): “Line graph showing global temperature anomaly 1880-2020, with overall warming trend accelerating after 1980”

Caption: “Data from NASA GISS. Note the particularly sharp increase in the last two decades.”

Universal resource: Link to Excel file with all temperature data points, allowing students to create their own visualizations or run statistical analyses.

Why this works: The alt text conveys what someone sees immediately—a warming trend. Students who need specific years or exact temperature values can access the spreadsheet, just as sighted students would need to examine the graph closely for those details.

Example 2: Anatomy Course – Detailed Heart Diagram

What a glance shows: The heart’s basic four-chamber structure. Alt text (176 characters): “Heart cross-section showing four chambers and major vessels, with blood flow indicated by arrows from body through right side, to lungs, returning to left side”

Caption: “Simplified cardiac anatomy. For detailed valve positions and vessel names, see the structured outline below.”

Universal resource: Downloadable outline with detailed anatomical descriptions, organized hierarchically (chambers, valves, vessels, blood flow path).

Why this works: The alt text provides the main structural understanding. Students needing to memorize specific valve names or trace exact blood pathways get that information in a format everyone can use effectively.

Example 3: Statistics Course – Multi-Variable Scatter Plot

What a glance shows: There’s a relationship between variables with some grouping. Alt text (163 characters): “Scatter plot of income vs. education level, showing positive correlation with distinct clustering by geographic region.”

Caption: “Data from 2020 Census. Regional patterns are particularly pronounced in urban areas.”

Universal resource: CSV file with all data points, allowing students to run their own statistical analyses or create alternative visualizations.

Why this works: The alt text conveys the main pattern visible at a glance. Students doing statistical analysis need the raw data anyway—making it available to everyone is simply good practice.

Want to learn more about the basics of writing alt text? Check out our blog at the link below.

Accessiblü Blog: Mastering the Art of Writing Alt Text

Common Misconceptions I’ve Encountered

“My alt text needs to describe EVERYTHING visible!”

No, it needs to convey purpose and context—what students understand from a quick glance. Detailed information belongs in alternative formats accessible to everyone.

“Complex mathematical equations need every symbol described.”

The alt text should convey what the equation does or represents. The full equation should be available in MathML or LaTeX format for all students who need to work with it.

“If I provide a data table, I don’t need alt text for the graph.”

Wrong. The graph and table serve different purposes. The graph shows visual patterns (which alt text should convey), while the table provides specific values (which everyone should be able to access).

“Making content accessible means creating separate materials for disabled students.”

This is perhaps the most damaging misconception. Universal design means creating materials that work better for everyone. When you provide data in multiple formats, all students benefit.

Practical Strategies That Actually Save Time

Strategy 1: The Purpose-First Approach

Before writing any alt text, I ask myself: “What do students understand from glancing at this image?” That’s my alt text. If they need more detail, I provide it in a format everyone can use.

This mental shift cut my alt text writing time by 75%. Instead of agonizing over describing every element, I focus on conveying the image’s purpose within the lesson context.

Strategy 2: Build Universal Resources into Course Design

When I create a complex visualization, I immediately create its text-based alternative for everyone:

• Graph → Excel file with data
• Diagram → Structured text outline
• Map → Geographic data table
• Flowchart → Step-by-step text process

This isn’t extra work—it’s materials you can reuse, share with colleagues, and that students consistently praise in evaluations.

Strategy 3: Use Templates Based on Purpose, Not Image Type

Instead of templates for “bar graphs” or “pie charts,” I use templates based on what the image teaches:

Comparison template: “[Visual type] comparing [what], showing [main finding]” Example: “Bar graph comparing study methods, showing active recall outperforms re-reading by 40%”

Trend template: “[Visual type] of [subject] over [time], showing [pattern]” Example: “Line graph of enrollment 2010-2020, showing steady growth until 2019 plateau”

Process template: “[Visual type] illustrating [process] with [number] stages: [main flow]” Example: “Flowchart illustrating protein synthesis with two stages: transcription in nucleus, translation in cytoplasm”

Relationship template: “[Visual type] showing relationship between [variables]: [main finding]” Example: “Scatter plot showing relationship between study time and grades: positive correlation with diminishing returns after 4 hours”

The Assessment Challenge: Maintaining Integrity While Ensuring Equity

For assessments, I apply the same principle: alt text provides the glance-level understanding without revealing what students need to analyze:

Testing data interpretation: Alt text: “Line graph showing monthly sales data with varying trend” What students figure out: The specific trend, turning points, and interpretation

Testing pattern recognition: Alt text: “Scatter plot with three distinct groupings of data points” What students figure out: What causes the groupings, their significance

Testing process understanding: Alt text: “Diagram of cellular respiration with three stages shown” What students figure out: What happens in each stage, energy yields

If your assessment requires students to extract specific data points, provide those points but test the analysis. If it requires visual pattern recognition that can’t be conveyed in text, develop an alternative assessment that tests the same learning objective through a different modality.

Building Your Practice: A Realistic Timeline

Week 1: Audit and Prioritize Review your next presentation. For each image, write one sentence about what students should understand from it at a glance. That’s your alt text starter.

Week 2: Create Universal Resources Choose three complex images and create alternative formats for everyone. Notice how this clarifies your teaching objectives.

Week 3: Refine and Template Develop your purpose-based templates. Test the glance principle—does your alt text convey what someone understands in 3-5 seconds of looking?

Week 4: Gather Feedback Share your materials with students. Ask everyone (not just those with disabilities) if the alternative formats help their learning.

Time Investment: The Real Numbers

When I first started, I tried to describe every detail of complex images. A single graph could take 20 minutes. Now, using the glance principle:

• Simple images: 15-30 seconds (just stating purpose)
• Complex visualizations: 1-2 minutes (conveying main message)
• Creating universal resource: 3-5 minutes (but benefits all students)
• Total for typical lecture: 20-30 minutes

The key shift: I’m not spending time writing lengthy descriptions only screen reader users will hear. I’m creating resources that enhance learning for everyone.

The Unexpected Pedagogical Benefits

Applying the glance principle and universal design has transformed my instructional design practice in ways I didn’t anticipate:

Clarity of Purpose: If I can’t write clear alt text conveying an image’s purpose, the image probably doesn’t belong in my materials.

Better Study Materials: Students consistently report that having data in multiple formats improves their understanding and retention.

Improved Collaboration: When data is available in accessible formats, students can more easily work together, regardless of their individual needs or preferences.

Enhanced Critical Thinking: When students have access to raw data, not just visualizations, they engage more deeply with analysis and interpretation.

Moving Forward: Your Action Plan

The path to accessible complex images isn’t about writing exhaustive descriptions—it’s about understanding what each image teaches and ensuring all students have access to that information.

Start with these principles:

1. Alt text conveys what someone understands from a glance (under 200 characters)
2. Every image must have clear purpose and context in your lesson
3. Detailed information should be available to everyone, not just those with disabilities
4. Universal design benefits all students, not just some

Remember, you’re not trying to paint a picture with words. You’re conveying the educational purpose of an image. If students need to examine it closely, provide that detailed information in a format everyone can use effectively.

The Bottom Line from Someone Who’s Been There

After many years in instructional design, I can say with certainty: the moment I stopped trying to describe every visual detail in alt text and started focusing on educational purpose, everything changed. My materials became more accessible AND more effective for all students.

The glance principle isn’t about doing less—it’s about doing what matters. When you provide the quick understanding through alt text and detailed information through universal resources, you’re not just meeting accessibility requirements. You’re practicing good pedagogy that benefits everyone.

Your students using assistive technology need the same thing all students need: a clear understanding of what images teach and access to detailed information when necessary. With the approach I’ve outlined here—born from real experience and refined through countless iterations—you can provide that without overwhelming yourself or shortchanging any student.

The goal isn’t to describe every pixel. It’s to ensure every student, regardless of how they access your materials, gets the information they need to succeed. That’s not just accessibility—that’s excellent teaching.