Data visualization presents information in visual formats rather than relying only on text or tables. These visuals can be interactive, allowing people to filter or select categories such as age, gender, or Minnesota county. We typically show results through bar charts, line graphs, maps, and other visual displays that make trends and patterns easier to recognize. Because visuals rely heavily on color to convey meaning, creating them requires careful attention to color use and accessibility.

Data visualizations help people quickly understand patterns, trends, and relationships—but they’re often designed to be seen. For users who rely on screen readers or have limited vision, alternative text (alt text) is essential to make visualizations accessible. 

This Tech Tip builds on our December 2025 newsletter article, “Data Visualization Accessibility: Focus on Color,” by exploring how to write effective alt text for charts, graphs, and maps. Whether your visualization uses color to convey meaning or includes interactive elements, alt text ensures that everyone can access the insights—not just the visuals.

Alt text basics

• Purpose: Alt text should describe the insight, not just the appearance.
• Tone: Use plain language and active voice.
• Length: Keep it concise but informative—1–2 sentences is often enough.
• Avoid: Redundancy, jargon, or overly technical descriptions.

Strategies for writing alt text

• Focus on the “why” and “what” of the data.
• Describe trends, comparisons, and outliers.
• Mention the chart type only if it helps understanding (e.g., “A bar chart showing…”).
• Include context. What does the data show? Why does it matter?

Describing color in alt text

Color is often used to convey meaning—but not everyone sees color the same way. If color communicates something important, say so in the alt text.

Tips

• Describe what the color means.
• Use labels, shapes, or patterns in the visualization to support color differences.
• If color is decorative or redundant, you can skip it.

Tool-specific tips

• Tableau: Use the new customizable alt text features (Tableau Cloud 2023.2 new features, including editing automatically generated alt text).
• Power BI: You can provide alt text for any object on a Power BI Desktop report by selecting the object. See additional tips in the “Tips from the DAC Community” section below. 
• Static maps: The content surrounding the map should contain the essential descriptive text which conveys the map’s message. Include a title, caption, paragraph text, data table, or link to explain the map’s message. Tag the map as a single image (Figure) and add brief alt text. Describe the map’s purpose and key message and that it complements the surrounding content.

Example 1: Process Flow Diagram — Technology Modernization Funding Process

Alt text: A process diagram shows how public and internal ideas move through agency review to determine whether a project funding status. The steps are: 1. Idea submission (from public or internal sources); 2. Initial review by agency staff; 3. Assessment of existing funding; 4. If funding exists, the project proceeds with implementation; 5. If funding does not exist, the idea is evaluated for technology modernization funding; 6. Approved projects move forward with the goal of improving customer experience through updated technology.

• Contextual Tip: If this image is embedded in a document or web page that already explains the process in surrounding text, you can use a shorter alt text and rely on the context: “A process diagram shows how public and internal ideas move through agency review to determine whether a project already has funding or needs additional technology-modernization funding. See surrounding text for detailed steps.”

Why this works

• Insight-focused: Describes the purpose and flow, not just shapes or icons.
• Concise but informative: The main message is captured in a short paragraph with a clear step-by-step breakdown.
• Plain language: No technical jargon.
• Focused: Does not over-explain visuals (e.g., icons, arrows) because they’re decorative.

Example 2: Pie Chart — Favorite Fruit

Alt text: Pie chart showing that apples are the most favorite fruit (8 votes), followed by oranges (5), bananas (4), and pears (3).

Why this works

• Insight-focused: Highlights the ranking and key comparison, not colors or shapes.
• Concise: Once sentence. Conveys the meaning of the data, not colors or slice shapes.
• Plain language: No technical jargon. And active voice.
• Color not required: Colors don’t convey meaning beyond labeling, so they’re not mentioned.

Tips from the community

Digital Accessibility Coordinators (DACs) from across state agencies shared real-world strategies on creating alt text for data visualizations:

Focus on the Data Story: “When we make alt text for data, we are tempted to stay strictly analytical. However, we are usually trying to tell the viewer something by adding complex charts/graphs. The alt text should focus on the story behind the data with reference to more in-depth explanation where applicable.” This aligns with guidance from Dr. Angela Young, a Certified Professional in Accessibility Core Competencies in the Washington/Baltimore area, in storytelling through accessible design. 

Practical Alt Text Strategies for Power BI and MS Access: “Add alt text that provides context and highlights the visualization's most important details. The alt text should communicate the main message and be as informative as the chart itself. Alt text should be included for every object that provides meaningful information in the report. When creating the alt text, think about how you would describe it to someone you're having coffee with.” Tips:

• Focus on the message, not the mechanics: Instead of describing the chart type (e.g., “a bar chart with five bars”), explain what the data shows (e.g., “Sales increased steadily from January to May, peaking in April”).
• Summarize trends or comparisons: Highlight patterns, outliers, or key comparisons that are visually obvious to sighted users.
• Include context: Mention what the data represents (e.g., “Monthly IT spend by division”) so users understand the scope.
• Avoid redundancy: Alt text can be shortened or omitted if the same information is already provided in surrounding text or captions.
• Use plain language: Keep it clear and concise—typically one to two sentences.

And don’t forget: Alt text does not update automatically. If the visualization is revised or updated, you must manually update the alt text to ensure it accurately reflects the current content

Closing

Alt text helps make data visualizations accessible to more people—including those who use screen readers or prefer non-visual formats. By describing what the data shows and why it matters, you make your insights available to everyone.