Typography Fundamentals for Slide Design

Why font choices, weights, spacing, and hierarchy shape the readability and impact of your presentations — and what to pay attention to when editing.

Font Families: Serif vs Sans-Serif

Fonts fall into two major categories. Serif fonts (Times New Roman, Georgia, Noto Serif) have small decorative strokes — serifs — at the ends of letters. Sans-serif fonts (Arial, Inter, Noto Sans, Helvetica) don't. In presentation design, sans-serif fonts are generally preferred for their cleaner appearance and better readability at large display sizes. Serifs work best for long-form body text in printed documents, where they actually aid horizontal eye-tracking, but at the large sizes used in slides, the serifs become visual clutter.

When editing slides, matching the original font family is critical. If the original deck uses Inter and you replace text with Arial, the difference in letter spacing and character proportions will be visible even to viewers who can't articulate what's wrong. The AI OCR in this editor detects the font family automatically, but if the exact font isn't available in the browser, it falls back to the closest match. Always check the result.

Font Weight: More Than Bold

Most people think of fonts as having two weights: Regular and Bold. Professional font families offer many more: Thin (100), ExtraLight (200), Light (300), Regular (400), Medium (500), SemiBold (600), Bold (700), ExtraBold (800), Black (900). Skilled designers use these intermediate weights to create subtle visual hierarchy — a section heading in SemiBold pairs naturally with body text in Regular, creating a clear distinction without the heavy visual impact of full Bold.

When replacing text in a slide, matching the exact weight matters more than most editors realize. A heading set in SemiBold replaced with regular Bold will look noticeably heavier than the surrounding headings, breaking the visual consistency of the deck. Cycle through the available weights in the sidebar weight selector and pick the one that looks right, not just one that's "close to bold."

Letter Spacing (Tracking) and Its Visual Impact

Letter spacing — formally called tracking — is the uniform adjustment of space between all characters in a line of text. It's measured in pixels or em-units, and it has a profound effect on the visual feel of text, especially in headings and titles.

Tight letter spacing (negative tracking) creates a dense, impactful feel often used for bold display headlines. Wide letter spacing (positive tracking, sometimes called "loose tracking") creates an airy, elegant feel often used for subtitles and small-caps captions. Default tracking (0) is standard for body text.

Letter spacing is the most-overlooked parameter in slide editing. Two text blocks using the same font, size, and weight can look completely different if their tracking values differ by even 1-2 pixels. After running AI OCR, always glance at the letter-spacing slider and compare your replacement text against unedited reference text. A 0.5-pixel adjustment is sometimes the difference between an edit that looks perfect and one that looks slightly off.

Visual Hierarchy: Guiding the Reader's Eye

Visual hierarchy is the principle of arranging text elements so the most important content draws attention first. In slides, hierarchy comes from four signals: font size (larger = more important), font weight (bolder = more important), color contrast (higher contrast = more important), and spatial position (top and center get more attention than bottom and corners).

When editing, it's crucial to preserve the existing hierarchy. If you replace a heading with new text, ensure the size, weight, and color match other headings in the deck. If you replace body text, ensure it stays visually subordinate to the headings above it. Breaking hierarchy — even slightly — is what makes professionally-designed slides start looking amateurish. Worse, it's a hard problem to debug after the fact: the reader knows something looks off but can't pinpoint why.

Practical Typography Rules for Slide Editing

1. Never use more than two font families in a single presentation. One for headings, one for body text. Using more breaks the visual unity of the deck.
2. Ensure sufficient contrast between text and background. Black text on white is maximum contrast. For colored backgrounds, use a contrast-ratio checker — text at 4.5:1 contrast or better is the WCAG accessibility standard.
3. Avoid text smaller than 18px for projected presentations. For handouts and on-screen reading, 14px is the minimum for body text. Smaller text loses readability the moment the viewer steps back from the screen.
4. Use line height (leading) of 1.3-1.6× the font size for optimal readability in multi-line text. Tighter than 1.2 feels cramped; looser than 1.7 makes lines feel unrelated.
5. Left-align body text. Center alignment is appropriate only for short headings, titles, and decorative captions — never for paragraph-length body content, where it produces "ragged" left edges that are exhausting to read.

Common Typography Mistakes in Edited Slides

Three mistakes show up over and over in edited slides, all easy to avoid once you know to look for them:

• Replacing a heading with text that's the right font but the wrong weight. Causes the section structure to feel inconsistent. Fix: cycle through the weight selector until the heading reads at the same visual prominence as other headings on the same slide.
• Pasting text that includes hidden character formatting. Especially common when copying from web pages. Always retype the replacement directly in the editor instead of pasting from elsewhere.
• Using condensed or extended variants of a font without realizing it. Many font families have width variants (Condensed, Extended) that look like the regular version but have totally different proportions. Mismatching width variants is one of the most visually jarring errors.