Teaching Hub

Five Rules For Engaging, Legible Presentation Slides

by Xabier Granja, Department of Modern Languages and Classics

Picture this: you are teaching a content class that is not based on visual material. Maybe you cover centuries-old literary works or political movements that did not spark a major artistic style, so you have to rely on text.

We live in an age where 92% of teens interact online on a daily basis using all sorts of devices and, in following the evolution of the Internet as a whole, graphical content now reigns supreme (it is no wonder infographics have become so popular). Semester after semester, a growing number of students seem increasingly disconnected, or maybe they are having difficulty grasping concepts that could benefit from some visual aid.

So you decide to create a slide presentation as a manageable way to make your lessons more engaging and clarifying. You make the slides, you use them in class, and soon you realize they do not seem to be helping much, or at all. Due to your lack of results, you give up: “PowerPoint” was simply not useful for your class after all. Right?

Wrong. I get it. I went through those same steps that most of us educators go through at some point in our careers while we try to adopt technology in our classroom. It is never easy – no matter what anyone tells you — to effectively integrate technology into your instruction.

It requires proper design, planning, and execution that will likely evolve by applying lessons over years of teaching. It took me the better part of a decade to realize that the problem was not PowerPoint but my own poor understanding of visual acuity and unrealistic expectations for the average human attention span (I guess not everyone is as fascinated about gender issues in the early 1600s as I am).

Over the past year, I have finally managed to make engaging and effective presentation slides because I now pay attention to one element that is shockingly often ignored: legibility. The more presentations I give, the more feedback I receive about the clarity of my slides and how much easier it is to follow the content I am showcasing.

Likewise, the more presentations I attend, the more I realize many scholars have real difficulties in condensing (and editing!) the information they want to convey in order to create quality materials for their classes, conferences, and other events.

How to Make Better Slides

In this post, I will give you some basic notions of what design flops to avoid and a simple set of five rules that yield engaging presentation slides that are legible, clear for your students, and simple to create. Adhering to these rules will ensure your presentations are effective, legible and most of all, engaging:

  1. Write no more than 40 words per slide.
  2. Avoid font sizes smaller than 28-point.
  3. Use black text on a white or a light grey background.
  4. Use red, blue, or green colors for highlights.
  5. Use pattern repetition throughout your presentation.

You can get started with this SamplePresentation!

Keep Text Brief and Legible

Let’s start with a common occurrence. How often have you attended a presentation, class or conference where you faced something like this:

Lorem ipsum text, which is a pseudo-Latin text used in web design, typography, layout, and printing in place of English to emphasise design elements over content. It's also called placeholder text

If you read Lorem ipsum and did not bother with the rest of the page, I would not blame you. The human brain has been trained for millennia to recognize patterns in the natural world — the kind of mental categorization that leads to phenomena like Pareidolia. It is only natural, then, that after seeing the first obvious two words, the rest immediately became nothing more than 4 rectangular blobs.

Regardless of whether the average attention span is really shortening to about 8 seconds or not, most people look at that slide and their attention turns to the shapes in it — it is your evolutionary predisposition. That slide’s text excess is ineffective because the mind cannot process the sudden information overload, regardless of your interest on the content.

How do we fix this?

Editing the content to the most important aspects and cutting out everything else is vital for an effective slide — brevity enhances communication, as different publications have already explored.

Use Color and Contrast

Sometimes presenters gravitate towards gradients. The color shift captivates our eyes’ natural affinity for changes in color and brightness. This shorter slide is more digestible but has lost contrast. If visual aids are hard to read, the mind wonders again. Your student is now no longer listening or paying attention but focusing on discerning the shape of that single rectangle blob.

Lorum ipsum text with a blue background that fades to white at the top of the slide

So, if gradients often fail at making things interesting, a more captivating graphical background, in some way related to the content, would surely do the trick, right? We can even blur it to increase legibility and, following the latest fashion, use a modern white-text-on-dark approach:

white lorum ipsum text with an out-of-focus image background

Now that is a striking slide. Your audience is now paying attention. The problem is, they are focused on the picture and not the text. It is visually engaging, so much so that colors and brightness have overtaken the main goal: content.

Over the past few years, the trend has been to create impact without detracting from the content: white-on-black has become the new king.

lorum ipsum in white text with an all black background. two of the filler text words are in red font

Bold. The frame of the display melts away, white text floats on the screen. Now the text is striking, there are no distractions, your mind is predisposed to read it, its attention focused on the paragraph. You even highlighted part of it in red for a more visceral contrast, because science proves human eyes are designed to see red and green better than blue.

There is only one small problem. This is how your striking slide looks in real life:

image of the previous image projected onto a screen in a UA classroom

The issue? Your desktop or laptop screen consists of a dark LCD panel where LEDs behind it light up pixels, and so black looks quite dark while whites shine through with force. Most presentation screens, however, are made of silvery-white fabric, because this material renders projected images best. When projected, your black becomes light grey and contrast goes out the window: the white text is barely readable, and the red highlight is illegible.

You could argue that sometimes you know that you will have a digital screen for your presentation, but considering that most consumer-grade displays are only capable of outputting 100-300 nits (unless you have a fancy HDR-capable system that outputs at 1000 nits with local dimming), the few white pixels that comprise your text will not light up much.

There are plenty more problems with displaying white-on-black text, and it gets even worse for anyone in your audience who happens to suffer from astigmatism.

We can fix this by making three simple changes:

  • Return to a light background.
  • Make the text even shorter than it was before.
  • Use a sharper font (e.g., Arial) that’s larger and easier to see.

Some will appreciate this clean aesthetic, others will find it boring or unexciting. Not to worry! You can add a light background to make your slide more interesting, while still maintaining legibility and contrast.

Light grey is preferable, as it will not greatly decrease contrast while reducing the light scattering that your eyes struggle with on harsh black/white projections:

the same slide as above but with a light grey background and a few words in red and blue font

This slide avoids all the problems mentioned up to this point. The light background takes into account that it will be projected on a light fabric screen that will render it slightly lighter, perceptually melting away while avoiding the ‘clinical white’ feeling that displeases many. The same paragraph was cut in two main points, for a total of 34 words on the screen that approaches the character limit for maximum effectiveness (40 words).

Let’s see how this slide displays in real life:

image of the slide described above projected onto a UA classroom screen

Notice how the big font, paired with colors that strongly contrast amongst themselves creates a very legible slide, even in an environment where lighting is not doing us any favors. I chose blue instead of green because it happened to have more contrast on this screen, which points to the fact that while the theory is helpful (e.g., green is easier to read), you need to take into account the projection method, surface, and room for best results.

If we switch back to the now popular white-on-black style, the slide disintegrates:

the same slide as a above, but with white font on a black background

White-on-black has become white-on-grey and is less legible than before. The blue highlight is now barely so but fares better than the red one, which is practically invisible. Does this mean that we should never use a dark background for improved legibility? Not really – you can effectively use this style for an elegantly designed, striking slide that aims for impact, not content.

This implies the use of very big fonts and graphical elements to create a sensation, instead of communicating content through text.

This slide makes much more efficient use of the picture we saw earlier, and it becomes engaging because it focuses on impact, not content. Because slides are free and you do not need to pack everything in one chunk, this impact slide is easy to read in an instant, full of contrast, memorable.

Both the black and white background engage your audience, and while both hold up quite well upon being projected, the lighter one displays better.

Repeat Design Patterns

Finally, if you do have images that you can use, avoid shocking your audience with moving elements flying around the screen. The brain focuses on the changes, not on the content, and there is more potential for confusion than there is for attention. The human mind, as initially stated, is used to pattern recognition: use a repetitive structure that offers few changes, where your audience cannot get lost because they will instinctively know what to expect.

The following is an example of one of my recent conference presentations, following all the indications in this post:

a sample of the author's actual presentation slides


Whether you are presenting research at a conference, showcasing points of interest to your colleagues, or teaching a class, different slide styles fit a variety of scenarios and it is your responsibility as the communicator to figure out how to do so most effectively. Most of the time you do not have control of where you will display your slides, so it is best to be proactive and default to best practices to avoid any potential complications.

Hopefully, this post gives you a few pointers as you design your next slide presentation. There are plenty of resources online for templates, whether paid or free, and their success at engaging audiences varies wildly.

My recommendation? Create your own template from scratch and reuse that template ad-infinitum. Soon it will become your own style and you will instinctively know exactly where to put elements. Adhering to the simple set of five rules will ensure your slides are effective, legible and most of all, engaging.