motion-typography

name	motion-typography
description	Use when type moves or changes over time — animated headlines, kinetic type, text transitions, animated or responsive logotypes, scroll-driven text effects, typing/counting animations, variable-font axis animation, or loading and streaming text. Also use when motion is making text hard to read, causing discomfort, or failing reduced-motion and accessibility requirements.

Motion typography

Type on screen is not fixed. Once type moves, it acquires a time dimension the print canon has nothing to say about — and a set of accessibility obligations that static type does not carry.

1. When to invoke

• Animated headlines, kinetic type, text reveals or transitions.
• Animated, flexible, or generative logotypes.
• Scroll-driven or scroll-linked text effects.
• Typing, counting, or streaming text (including LLM token streaming).
• Animating variable-font axes.
• Someone reports motion sickness, discomfort, or unreadable moving text.

Do not invoke for static composition (typography-layout-systems) or for general UI text (ui-component-typography).

2. Required context

• What the motion is for — meaning, feedback, continuity, or decoration. Only the first three are usually defensible.
• Whether the text is read during motion or only before/after it.
• Duration, and whether it loops or auto-starts.
• Whether the user can pause, stop, or skip it.
• Whether motion is scroll-linked (user-controlled) or time-based (autonomous).
• Reduced-motion and vestibular-disorder considerations.

3. Invariant principles

• Text being read must not move. Motion during reading defeats the saccadic process entirely — the eye cannot fixate on a moving target and cannot execute reliable return sweeps. Animate into a resting state, then stop.
• Respect prefers-reduced-motion. Not optional. Provide a meaningful reduced state — usually an instant cut to the end state, not a broken one.
• WCAG 2.2.2 (Pause, Stop, Hide): any moving, blinking, or scrolling content that starts automatically, lasts more than 5 seconds, and is presented alongside other content must have a mechanism to pause, stop, or hide it.
• WCAG 2.3.1 (Three Flashes or Below Threshold): nothing may flash more than three times per second. This is a seizure risk, not a preference.
• Motion must not be the only carrier of meaning. If an animation communicates state, that state must also be available statically.
• Layout must not shift as a side effect. Animating a property that changes text metrics reflows the page and damages CLS.

4. Context-dependent heuristics

Animate the cheap properties. transform and opacity are composited and don't trigger layout. Animating font-size, font-weight, letter-spacing, or width reflows text on every frame — expensive and visually unstable.

Want	Animate
Reveal / entrance	opacity, transform: translate
Emphasis	transform: scale
Weight change (variable font)	font-variation-settings — but see reflow warning
Position along scroll	transform, via scroll-driven animation

Variable-font axis animation is the genuinely new capability, and the trap is that wght and wdth change advance widths, so animating them reflows the line. Either reserve the space, animate a display element that owns its line, or accept the reflow only where nothing else depends on the metrics. See variable-fonts.

Duration. Text reveals want to be fast — roughly 150–300ms for a single element. Anything a user waits through before they can read is a tax. Stagger across multiple elements sparingly; a long stagger delays comprehension of the last item.

Scroll-driven vs. time-based. Scroll-linked motion is user-controlled, so it sidesteps most of 2.2.2 — the user can always stop by not scrolling. Time-based autonomous motion carries the full obligation. Prefer scroll-linked where the effect allows.

Streaming text (LLM output, live captions) is a special case: it's continuously changing text the user is reading. Keep the already-rendered text stable — never re-flow or re-wrap what's been read. Append only.

Layering over time. Type on Screen's additive layering — styles within a family acting as separate structural or decorative elements — extends naturally to motion: layers can arrive in sequence rather than all at once. Carter's Walker (1995) uses five "snap-on" serif styles as composable layers while keeping a unified look.

Logotype motion. Animated and flexible logotypes are a legitimate genre, but the resting state must be the canonical mark. Motion is an entrance, not the identity.

5. Failure patterns

Pattern	Cause	Fix
Users can't read the animated headline	Text moving while being read	Animate in, then rest
Motion sickness reports	No reduced-motion handling	prefers-reduced-motion
Reduced-motion state shows nothing	Animation is the reveal; disabling hid the text	Reduced state = final state, instantly
Page jumps during a weight animation	wght changes advance widths	Reserve space or animate transform
Carousel text can't be stopped	Auto-starting, >5s, no control	Add pause/stop (2.2.2)
Janky animation	Animating layout-triggering properties	transform / opacity
Streaming text re-wraps as it arrives	Re-laying out rendered content	Append-only rendering
Long stagger delays reading	Too many staggered elements	Shorten or group
Flashing emphasis effect	Rapid opacity toggling	Never exceed 3 flashes/second (2.3.1)

6. Evaluation procedure

1. Ask what the motion is for. If the answer is "it looks nice", weigh it against its cost honestly.
2. Confirm no text is expected to be read while moving.
3. Set prefers-reduced-motion: reduce and verify the result is usable and complete, not empty or broken.
4. If motion auto-starts and runs >5s alongside other content, confirm a pause, stop, or hide mechanism exists (2.2.2).
5. Count flashes per second — must be ≤3 (2.3.1).
6. Record a performance profile. Confirm no layout thrash per frame.
7. Measure CLS with the animation running.
8. For variable-font axes: confirm no reflow, or that reflow is contained.
9. For streaming text: confirm rendered text never re-wraps.
10. Test on a low-end device — motion that's smooth on an M-series Mac may not be.

7. Output format

Purpose: <meaning | feedback | continuity | decoration>
Motion: <property> over <duration> <easing>, <scroll-linked | time-based>
Read-during-motion: <no | yes → defect>
prefers-reduced-motion: <behaviour> — usable: <yes/no>
WCAG 2.2.2 (>5s auto): <n/a | control provided>
WCAG 2.3.1 (flashes): <n>/sec
Layout impact: reflow <yes/no> · CLS <n>
Tested on low-end device: <yes/no>

8. Examples

Hero headline that animates its variable-font weight from 300 to 700 on load.

Two problems. The wght axis changes advance widths, so the headline reflows on every frame — the text visibly re-wraps and it shows up as CLS. And under prefers-reduced-motion: reduce the current implementation skips the animation and leaves the element at its 300 start value, so reduced-motion users get the wrong design rather than a calmer one.

Fix: animate opacity and a small translateY for the entrance instead, and set the final 700 weight statically so no metrics change. Reduced-motion state becomes the final design shown instantly. If the weight animation is essential to the brand, give the headline a reserved fixed block so reflow is contained.

Streaming assistant response.

The text is being read as it arrives, which is the one case where moving text is unavoidable. The rule is that already-rendered text must never move: append new tokens without re-wrapping what's above. Avoid text-wrap: balance on the streaming container — it rebalances the whole block on every update, so every line the user has already read jumps. Apply it only once streaming completes.

9. Counterexamples

• ❌ "Animate the paragraph text in word by word, it looks premium." — Delays reading and defeats fixation.
• ❌ "We respect reduced-motion — we disable the animation." — If the animation was the reveal, disabling it hides the content. The reduced state must be the final state.
• ❌ Animating letter-spacing or font-size for a hover effect. — Reflows text on every frame.
• ❌ "It's a carousel, users can wait for it to come around." — 2.2.2 requires a control.
• ❌ "The animation communicates that the item is new." — Motion alone can't carry meaning; provide a static indicator too.
• ❌ Applying text-wrap: balance to text that is still streaming in.
• ❌ Testing motion only on a high-end laptop.

10. Source citations

• Lupton (ed.), Type on Screen — primary book source. Motion and temporal typography; animated, flexible, and generative logotypes; kinetic alphabets; logo transition; type and code (Processing, Scriptographer, SVG type generators); additive layering, where each style in a family acts as a distinct structural or decorative element — Matthew Carter's Walker (1995) and its five "snap-on" serif styles; "typography is forever in motion — and never more so than now."
• WCAG 2.2 §2.2.2 (Pause, Stop, Hide), §2.3.1 (Three Flashes or Below Threshold), and prefers-reduced-motion as the mechanism for §2.3.3 (Animation from Interactions, AAA). Outranks aesthetic preference.
• MDN — prefers-reduced-motion, scroll-driven animations, font-variation-settings.
• Hochuli, Detail in Typography — the reading process (saccades and fixations) that moving text disrupts; the reason "text being read must not move" is a physiological claim, not a stylistic one.