Contrast and Accessibility in Slide Design

Every audience includes people who see, hear and process information differently. In a lecture theatre or online course, that might be students with low vision, colour vision deficiency, dyslexia, or who are watching on a cracked phone screen in bright sunlight. Accessible presentation design means building slides that work for all of them. The good news is that most of the fixes are simple, and they make slides clearer for everyone.

Read the video transcript

Every audience sees, hears and processes information differently. A few simple fixes make your slides work for every viewer, and clearer for everyone.

Low contrast is the most common problem, and one of the easiest to fix. Aim for four and a half to one for normal text, and three to one for large text.

Use near-black text on light backgrounds, put a solid panel behind text on photos, and always test with a checker.

Some viewers can't tell red from green. Give each status a label and an icon, and let colour be an extra cue, not the only one.

Big, plain, left-aligned text reads well in a room and on a small screen. Body text at 24 point or larger, headlines at 36 or larger.

When a deck becomes a video, turn on captions, and let the voice explain what a chart shows, not just say 'as you can see here'.

Accessible slides make better videos. On Pro, AI directs the video, timing animation to your narration. Try Basic first at powerpoint2vid.com.

This guide covers the practical side: contrast, text, colour, layout and video.

Why accessibility matters for slides

Accessibility isn’t just a compliance box. Universities and many workplaces have policies that expect teaching and training materials to be accessible, and the Web Content Accessibility Guidelines (WCAG) are a common reference point. But the more practical reason is that accessible slides are better slides.

High contrast helps on a washed-out projector. Large text helps on a small screen. Clear structure helps someone tired at the end of a long day. Designing for the edges improves the middle.

Contrast: the foundation of accessible presentation design

Contrast is the difference in brightness between text and its background. Low contrast is the most common accessibility problem in slides, and one of the easiest to fix.

The numbers to aim for

WCAG sets out contrast ratios at the AA level:

• 4.5:1 for normal text
• 3:1 for large text (roughly 18pt and above, or 14pt bold and above) and for important graphical elements such as chart bars and icons

Use a contrast checker to test your combinations. Many are available online, and some design tools have one built in.

Common contrast problems

• Light grey text on white
• Mid-tone text on a coloured background
• Text over a photo with no overlay
• Brand colours that look great as shapes but fail as text
• Placeholder text styles left in a pale default colour

Quick fixes

• Darken text to near-black on light backgrounds.
• Use white or near-white text on dark backgrounds.
• Add a solid or semi-transparent panel behind text on photos.
• Keep a deeper version of your brand colour for text, and the lighter version for shapes.

Never rely on colour alone

Some viewers can’t tell certain colours apart, especially red and green. If colour is the only thing carrying meaning, those viewers miss it.

Before: A table of project statuses where on-track items are in green text and late items are in red text.

After: Each status has a label (“On track”, “Late”) and an icon, with colour as an extra cue.

The same applies to charts:

• Label series directly on the chart instead of relying on a colour legend.
• Use patterns, shapes or position as well as colour where series need telling apart.
• Highlight the important bar with colour and a label, not colour alone.

Text that’s easy to read

Size

Body text at 24pt or larger reads well in a room and on most screens. Headlines at 36pt or larger. Avoid going below 18pt for anything people need to read.

Font choice

Choose a clean, plain font with open letter shapes. Avoid script, condensed or very light fonts for anything longer than a few words.

Layout

• Left-align body text. Centred and justified text is harder to track, especially for readers with dyslexia.
• Keep lines short. Long lines across a wide slide are tiring.
• Use sentence case. All caps is harder to read in longer phrases.
• Leave space. Crowded slides are harder for everyone.

Structure and reading order

Some viewers use screen readers to access slide files. Slide structure helps them.

• Give every slide a unique title, using the title placeholder rather than a text box. Screen readers use titles to navigate.
• Check reading order. PowerPoint has a tool for viewing and changing the order in which objects are read. Look for it in the accessibility options.
• Add alt text to meaningful images. Describe what the image shows and why it matters. Mark decorative images as decorative.
• Use real lists and tables, not shapes arranged to look like them.

PowerPoint also includes an accessibility checker that flags many of these issues. It’s worth running before you share a deck.

Motion and timing

Animations and transitions can help focus attention, but too much movement is distracting, and some people are sensitive to it.

• Use simple builds that reveal one point at a time.
• Avoid flashing or rapidly moving elements.
• Give each slide enough time to be read and understood.

Accessible presentation design in video

When a deck becomes a video, a few more things matter.

• Captions. Burned-in captions help viewers who are deaf or hard of hearing, those watching without sound, and people reading in a second language. Keep the slide itself light on text so captions don’t compete with it.
• Narration that describes the visual. Viewers with low vision benefit when the voice explains what a chart or diagram shows, not just “as you can see here”.
• Readable at small sizes. Video is often watched in a small window. Larger text and stronger contrast hold up better.
• Steady pacing. Choose a speaking speed that lets every slide be read before it changes.

There’s more on captions in captions on presentation videos.

Sample narration that describes a chart

Slide headline: “Attendance rose in every week after we moved lectures online”

This chart shows weekly attendance across the semester. The first six weeks, in grey, were in person. The next six, in blue, were online. Each online week is higher than any in-person week. The biggest jump came in week seven, right after the switch.

A viewer who can’t see the chart clearly still gets the whole point.

Quick checklist

• Text contrast at least 4.5:1, large text and key graphics at least 3:1
• No meaning carried by colour alone
• Body text 24pt or larger, left-aligned
• Plain, readable fonts
• Unique title on every slide, in the title placeholder
• Alt text on meaningful images
• Reading order checked
• Accessibility checker run
• Captions on for video, and narration that describes visuals

Accessible slides make better videos

Every fix in this guide makes a slide video easier to follow: stronger contrast survives compression, bigger text reads on phones, and narration that describes visuals helps everyone. For more on how voice and visuals work together, see why people remember more from narrated visuals.

When your deck is ready, drop it into the PowerPoint to video converter. Turn on burned-in captions and choose a steady speaking speed. a.i. takes the director’s chair, designing each scene and timing the animation to the narration, so your accessible slides arrive as a clear, well-paced explainer. Watch the result at a small window size to check everything stays readable.