Presentation design: slides that support the speaker

At a conference presentation, the audience came to hear a person. The slides are a visual aid, not a document to be read on screen. When they try to be both, the audience reads ahead, stops listening and remembers neither.

The UK Government Digital Service built its presentation template so that the emphasis stays on the speaker, with each slide supporting one short line of text.¹ It also points out that slides are not always the right tool: text that needs approval can be sent separately, and a large diagram can be printed so people can be walked through it.¹ Good presentation design starts by deciding what the slides need to do, and what the speaker or a handout can do better.

Before opening PowerPoint, write down the main point you want to make. The same GDS advice says clarity comes from preparation, and suggests asking: what is the main point I want to make?¹ If you cannot say it in one sentence, the slides will not say it either.

Then plan the talk as a sequence of points, one per slide. In our own practice, we sketch the order on paper or sticky notes first, because it is far easier to move a note than to redesign twenty finished slides. Each slide headline should be a short statement that makes sense on its own, such as "Enrolment rose in all five districts", rather than a label such as "Results".

Research on multimedia learning explains why this works. Richard Mayer and Roxana Moreno summarise their findings as the multimedia principle: it is better to present an explanation in words and pictures than in words alone.² Their redundancy principle adds that people learn better from animation and narration than from animation, narration and on-screen text together.² Their research was on computer-based learning, but the lesson carries over to the conference room: a picture on the slide and the explanation in the speaker's voice is a stronger combination than a paragraph the speaker reads aloud.

W3C's checklist for accessible events and presentations gives the same practical advice: avoid putting lots of text or other content on slides.³ Digital.gov asks its event presenters to limit the amount of text to the main points.⁴ Detail belongs in the speaker's words, the speaker notes or a handout.

Conference rooms are large, screens are often small and projectors wash out colour. W3C recommends making text and important visuals big enough to be read from the back of the room, using an easy-to-read font and using a consistent design across slides to limit cognitive load.³ Microsoft's accessibility guidance for PowerPoint recommends a font size of 18pt or larger, familiar sans serif fonts such as Arial or Calibri, and sufficient white space.⁵

Contrast matters as much as size. The Web Content Accessibility Guidelines set a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text, defined as at least 18 point, or 14 point bold.⁶ These are minimums for screens, and a projector usually lowers contrast, so aim higher. W3C notes that some presenters prefer dark text on a light background in a lit room.³

• One idea and one short headline per slide.
• Body text at 18pt or more; headlines much larger.
• Dark text on a light background, or the reverse, with strong contrast.
• The same fonts, colours and positions on every slide.
• Plenty of empty space around each element.

A chart on a slide has seconds to make its point. The European Union's data visualisation guide advises starting with the purpose of the visualisation and the message you want to get across, then choosing the chart type that fits that message.⁷ On a slide, simplify further: show only the data that supports the point, label the key figure directly and state the finding in the slide headline.

Use real photographs from your own work rather than generic stock images, and choose ones that show the place, the activity or the result you are talking about. Microsoft advises that colour should not be the only means of conveying information, and that videos with dialogue should include closed captions.⁵ W3C also recommends avoiding blinking or flashing content, which could cause seizures.³

Accessibility helps everyone in the room, and it helps everyone who receives the file afterwards. Microsoft recommends giving every slide a unique title, adding alt text to visuals so people who use screen readers understand what is important, and checking that slide contents are read in the intended order.⁵ It also recommends using built-in slide designs, which help with reading order and colours.⁵

Accessibility also depends on how the slides are presented. W3C advises speakers to say all the information on each slide, including text and graphics, to avoid jargon, acronyms and idioms or explain them, and to avoid speaking too fast so that participants and interpreters can keep up.³ It also recommends providing slides and other materials to participants, interpreters and captioners as needed.³ For multilingual events in East Africa, sending the deck to interpreters early is one of the simplest ways to improve the session.

The last piece of GDS advice is the simplest: rehearse, and rehearse a lot.¹ Rehearsal shows which slides are too crowded, which transitions are confusing and where the talk runs long. Where possible, test the final file on the venue's equipment, check that fonts and videos play correctly, and bring a PDF copy as a backup.

Event organisers often set their own rules. Digital.gov, for example, asks presenters to submit slides five days before an event and to share only the approved slides during the session.⁴ Check the organiser's deadline, format and aspect ratio early, so the design is built for the screen it will be shown on.

• The main point written in one sentence
• One idea and one statement headline per slide
• Text at 18pt or more, in a clear sans serif font
• Strong contrast between text and background
• Charts simplified to the data that makes the point
• Unique slide titles, alt text and a checked reading order
• Slides sent to organisers and interpreters in advance
• A full rehearsal on the venue's equipment