Don’t Make My Mistakes: A Key Lesson on Alt Texts for Power BI & DataViz Contests

[KarinSzilagyi]

The Microsoft Power BI DataViz World Championships 2026 are here, and if you’re planning to participate, there’s one judging criterion that could make or break your entry: accessibility.

By the time I submitted my first DataViz contest report, it felt finished. I liked the result, had experimented with new techniques, and believed I had met all the judging criteria.

As we all know: Hindsight is 20-20.

Once the adrenaline subsided, the glaring mistakes appeared.
Alt text, in particular, didn’t hold up once I looked at it more closely. Multiple entries were missing entirely, and even where I had added alt text, I could tell that it felt wrong, though I couldn't tell yet why. 
I don’t have a time machine (yet, if you can see this, I’m still working on it), so I did the next best thing: studied and researched. Luckily for you, I’m sharing what I learned - so you don’t have to stumble into the same pitfalls I did.

What Alt-Text Really Is (And Isn’t)

Alt text (alternative text) is a spoken description of a visual element that screen readers use to convey information to users with visual impairments. 

When I worked on my contest submission, I completely misunderstood what that actually means. I knew alt text helps screen reader users, but I missed the crucial point.

My (wrong) assumption back then: Alt texts matter so screen reader users know whether the visual is worth interacting with.

The truth: Alt text is not a teaser. It’s main focus is not to help users decide whether to engage. For screen reader users, the alt text is the visual.

But it's even more important than the definition above implies. Alt text is:

• an accessibility bridge for screen reader users,
• a fallback when visuals fail to load, and
• unexpectedly, a design quality tool.

Forcing yourself to summarize a complex chart into one or two sentences quickly reveals whether the visual has a clear message or whether it’s overloaded with decorative or redundant elements. If you struggle to write good alt text, that’s often a signal the visual itself needs simplification.

Power BI Alt Text Support: What You Need to Know

What Supports Dynamic Alt Text

Almost everything in Power BI supports dynamic alt text (DAX-generated descriptions that change with your data):

• Nearly all native visuals (except Q&A and Key Influencers)
• Text boxes
• Shapes
• Buttons
• Bookmark and page navigation elements

What Doesn’t

• Q&A visual (which will be deprecated end of 2026)
• Key Influencers visual
• Grouped items. Some screen readers like NVDA treat groups as a single element when accessed via tab order, making alt text especially important! 

For non-native visuals (for example, visuals installed via Microsoft AppSource), support for dynamic alt text varies. Regardless of whether the alt text is static or dynamically generated, screen readers don’t always handle it in Power BI the way you might expect.

Until recently, I assumed text boxes didn’t need alt text since screen readers would read them anyway. I tested this with NVDA, and the results were humbling. If you navigate your report via tab order, NVDA will skip the content of the text box completely and only read out the title, subtitle and alt text (if present). Only if you hover over the text box with your mouse, NVDA will recognize the text inside the box and actually read it. 

Take this basic bar chart:

Without alt text, NVDA reads “No alt text’, ‘Total Sales by Year’ grouping.”

With tooltips enabled, users might get:

“Year twenty twenty-five. Total Sales. Seven hundred seventy-two thousand nine hundred forty-nine dollars.” I already forgot that number halfway through listening.

This shows why good alt text matters and what we actually need to help screen reader users navigate our reports and gain insights.

The Three Pillars of Great Alt Text

Whether you’re writing manually or using DAX, every good alt text needs three components:

• The Chart Type
  Clearly state what kind of visual or item you’re describing. Example: “Line chart showing…”

1. The Variables
   Briefly describe what data is being measured and the relevant context (filters, axis, timeframes). Example: “…monthly sales trends across product categories for 2025…” or “…sales by product category, filtered to Electronics department…”

1. The Key Insight
   The “so what?” The actual story your visual tells (direction, top/bottom, outliers, change vs prior/target). Example: “…with electronics showing a 45% increase in Q4, significantly outperforming all other categories.”

Complete example: “Line chart showing monthly sales trends across product categories for 2025, with electronics showing a 45% increase in Q4, significantly outperforming all other categories.”

Since data storytelling is a main judging criterion (and essential for professional reports), this doubles as a litmus test: If you can’t explain what the visual shows, does the visual actually matter? Consider whether there’s a better way to show the data.

Best Practices

• Keep It Concise but Complete: Brief enough to be digestible when spoken, comprehensive enough to convey essential information. Ideally aim for just one to two sentences.
• Use Proper Grammar: Alt text should flow naturally when read aloud.
• Reference Color When It Matters: Only mention color when it conveys data meaning that helps understanding. Example: “Heat map showing sales performance by region and quarter, with darker red indicating higher values, ranging from $500K (light) to $2.3M (dark red) in Q4 North America.” This also matters because not everyone who uses a screen reader is fully blind. Users with low vision may still perceive color or contrast to some degree, and describing the color scale can help them orient themselves, even if the visual appears blurred or incomplete.
• Avoid Redundancy: Don’t duplicate existing text or titles. If your title is “Q4 Sales by Region,” don’t start alt text with “This chart shows Q4 Sales by Region…”
• Never Include URLs: Screen readers spell out every character (“h-t-t-p-s-colon-slash-slash…”), which can be painful to listen to. More importantly, links in alt text aren’t clickable, so they’re useless. Include sources in your report text or footer where users can actually interact with them.

Implementing Alt Text in Power BI

Manual Alt Text

As mentioned above, nearly all visuals and elements in Power support both manual (static) and dynamic alt texts.

For static descriptions:

1. Select your visual
2. Format pane → General → Alt text
3. Enter your description

You have 250 characters to work with - make them count! Manual alt text works well for visuals with fixed insights and static data that aren’t affected by slicers or cross-filtering.

💡DataViz Contest Tip: Don’t let perfection get in the way of completeness. Since contest datasets are usually static snapshots, focus first on clarity, insight, and accessibility across the whole report. Having good alt text everywhere matters more than stressing over dynamic alt text where it isn’t needed!

Dynamic Alt Text

While manual alt text is often sufficient for contest submissions, real-world reports usually require dynamic alt text as data and filter context change. Dynamic alt text is generated through text measures and applied via the dynamic format pane.

💡Pro tip: Use DAX user-defined functions (UDFs) to keep alt text measures clean and maintainable. Let me know in the comments if you’d like a separate article on this!

Final Thoughts

The DataViz World Championships are a great learning opportunity to practice building accessibility into your reports from the start, instead of treating it as an afterthought that costs you points.

But more importantly: 16% of the global population has some form of disability. When you build accessible reports, you’re not just scoring contest points; you’re making your insights available to everyone who needs them. In professional settings (e.g. government reporting), accessibility often isn’t optional; it’s a requirement.

💡 Note: I’ve created a companion video showing how NVDA interprets visuals in Power BI with and without alt text. Watch the video to experience firsthand why alt text matters.

Ready to make your DataViz World Championship submission (or your next client report) more accessible?
Start with alt text. The judges - and your users! - will thank you. 

[Olayemi_Awofe]

This is so helpful

[Juless]

This is amazing! I would love an article on using UDFs for alt text!

[vivmueller]

Thank you very much for explaining this, also in the video! ❤️

[krishnakanth240]

An important reminder. 3 pillar framework (chart type + variables + insight) is practical and the NVDA example makes it clear. Thank you @KarinSzilagyi