Ux Mobile Responsiveness Audit

Mobile Responsiveness Audit Skill

How this skill behaves (read first)

This is an evaluative skill — it reviews existing work against mobile/touch standards, it doesn't generate. Flagging is safe, so it auto-runs and is built to be called as a validation step by generative skills whenever the target is mobile or responsive (the component family, screens, and flows all hand off here for their mobile context).

It owns the mobile/touch-adaptation concern in this repo. To avoid duplicating its sibling audits, it defers:

• WCAG ratios, screen-reader/assistive-tech, keyboard operability, alt text, captions → the accessibility audit. This skill judges physical touch ergonomics and layout adaptation, not AT compatibility or contrast math.
• Visual composition — hierarchy, spacing aesthetics, emphasis → the aesthetics audit.
• Usability, flow, and interaction logic → the heuristics audit.
• Content structure / navigation scheme → the information-architecture audit; type scale → ux-typography.

> Applicability gate: this audit only applies when the target is meant to work on mobile or across breakpoints. If a design is explicitly desktop-only (e.g. a complex internal admin tool with no mobile support), say so and skip — don't manufacture mobile findings.

Scope discipline. When invoked directly (the user named this audit), review only this concern — don't pull in sibling audits. It runs alongside other lenses only when an orchestrator (ux-design-review) or a generative skill calls it under docs/orchestration-policy.md, where it sits in Tier B — offered (only when the platform is mobile). Explicit scope always wins.

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What this skill changes vs. default behavior

By default, "is it mobile-friendly?" gets a vague answer — "make the buttons bigger," "it should be responsive" — with no threshold, no severity, and no systematic sweep. This skill forces:

1. Every finding names the violated principle (reflow, touch-target size, thumb reach, etc.) and gives the concrete threshold (44pt / 48dp, ≥8dp spacing, ≥16px body).
2. Severity rated by whether it blocks the task on the device vs. adds friction vs. polish.
3. A specific fix, not "optimize for mobile."
4. A systematic sweep of all seven areas, so issues beyond "small tap targets" — orientation locks, wrong keyboard types, gesture dead-ends, non-reflowing layouts — actually get caught.

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The framework — what to check and what a violation looks like

Work through each. Flag with principle, severity, fix.

1. Viewport adaptation & reflow

The layout must adapt to the viewport — fluid grids, flexible images, content that reflows and reorganizes — rather than a fixed-width desktop layout squeezed onto a small screen. (Responsive = one fluid layout with breakpoints; adaptive = distinct layouts per breakpoint. Either is fine; not adapting is the failure.)

Flag when: horizontal scrolling or content cut off at the edges; a fixed-width (px) container that doesn't shrink; tiny zoomed-out desktop layout; elements overlapping or colliding between common breakpoints; images that don't resize proportionally; multi-column layouts kept on narrow screens instead of stacking vertically.

• ❌ A 1200px content frame on a 390px phone → user must pinch-zoom and scroll sideways to read.
• ✅ Content reflows to a single fluid column; images scale; nothing exceeds the viewport width.

2. Orientation resilience

Users hold devices both ways. Essential features must work in portrait and landscape; orientation changes should be purposeful, not breaking.

Flag when: the layout breaks, clips, or leaves dead space when rotated; core functionality is locked to one orientation without a real reason; a keyboard-heavy or video screen is forced to portrait when landscape would serve better; auto-rotation fires where it disrupts the task.

• ❌ Rotating to landscape hides the submit button below an un-scrollable fold.
• ✅ Portrait is the primary design; landscape reflows and keeps every essential action reachable.

3. Touch-target size & spacing

Fingers and thumbs are imprecise. Targets must be large enough and spaced enough to hit reliably — especially for adjacent contradictory actions (Save vs. Delete).

Flag when: interactive targets below the platform minimum — iOS 44×44pt, Material 48×48dp (WCAG floor 24px, but the platform minimums are the working target); less than ~8dp/16px spacing between tappable elements; corner targets the same size as central ones (corners are harder — aim larger, ~12mm vs ~7mm center); destructive and confirming actions tiny and adjacent.

• ❌ A 28px icon button row with 2px gaps; "Delete" sits flush against "Save."
• ✅ ≥44pt/48dp targets, ≥8dp spacing, extra size for corner/contradictory actions.

4. Thumb reachability & one-handed use

People operate phones one-handed and prefer the screen center; hands obscure the interface and shift grip constantly.

Flag when: primary actions stranded in hard-to-reach top corners; destructive actions in the easy-tap thumb zone where they're hit by accident; key content jammed against the top edge; no bottom padding so content can't scroll to the comfortable center; right-edge-only button placement.

• ❌ The main CTA pinned top-right; a "Delete account" button in the bottom-center thumb sweet spot.
• ✅ Primary actions within thumb reach (lower-center / bottom sheet); destructive actions guarded or out of the accidental-tap zone; content scrollable to center.

5. Mobile input ergonomics

Typing on mobile is slow and error-prone (≈41% type two-thumbed). Match the input method to the data and minimize manual entry.

Flag when: a generic keyboard where a contextual one fits (no numeric keypad for phone/PIN, no "@"-optimized keyboard for email, no URL keyboard for web addresses); no autofill/autocomplete for name, address, email, payment; free-text fields where selection controls (picker, radio, toggle) would do; long forms not chunked across steps; no OTP autofill / card-scan where available.

• ❌ Phone-number field opens the full QWERTY keyboard; address typed from scratch with no autofill.
• ✅ Numeric keypad for numbers, email keyboard for email; autofill and selection controls reduce typing.

6. Gesture safety & discoverability

Gestures are invisible — they have discoverability, consistency, and accessibility limits. They should supplement, never solely carry, an action.

Flag when: a critical action is reachable only by a hidden gesture (edge-swipe menu, long-press) with no visible control; non-standard gestures redefining system conventions; complex multi-finger gestures required (exclude users with motor/dexterity limits); activation on touch-start rather than touch-end-within-target (accidental triggers).

• ❌ The only way to delete an item is an undiscoverable left-swipe; no button alternative.
• ✅ Swipe offered as a shortcut alongside a visible control; only simple, conventional gestures are required.

7. Mobile readability & content priority

Small screens used outdoors and in motion demand readable text and a ruthless first-screen priority — adapt content for mobile, don't just shrink the desktop.

Flag when: body text below 16px; mobile line length outside ~30–40 characters; display typefaces at small sizes; the screen tries to show everything instead of leading with the primary task; secondary/tertiary functions crowding the first view instead of living below the fold or behind menus; the mobile version feels like a different product from desktop (inconsistent patterns, colors, controls).

• ❌ 12px body text, four competing CTAs above the fold, a desktop-only color scheme.
• ✅ ≥16px body, one clear primary action first, secondary actions deferred, consistent with the desktop product.

> Tension note: mobile pushes toward fewer, larger elements (targets, type, one primary action) while product owners push to surface more. Resolve toward the device reality — limited space and imprecise touch — and defer extra density to progressive disclosure rather than cramming. Where a fix would collide with the accessibility audit (e.g. target size, gesture alternatives), state it once and let accessibility own the AT/WCAG framing.

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Severity rating

| Severity | Meaning | |---|---| | Critical | Unusable on the target device — content cut off / horizontal scroll, targets too small to tap reliably, a critical action only via an undiscoverable gesture, or a core feature locked to an unavailable orientation. Fix before ship. | | Major | Significant friction users shouldn't have to absorb — targets below the platform minimum but still tappable, primary action outside thumb reach, wrong keyboard type, body text below 16px, layout that reflows poorly at a common breakpoint. | | Minor | Noticeable polish — slightly tight spacing, a non-ideal landscape layout, mild over-density, corner targets not enlarged. |

Rate by impact on completing the task on the actual device, not by how easy the fix is. A one-line keyboard-type change can still be Major if it blocks fast entry.

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Audit output format

## Mobile Responsiveness Audit — [Screen / Component]
Context: [device class / breakpoints · orientation · primary task, if known]

### Critical
- [Issue] — what's wrong → fix. (Principle: …)
### Major
- …
### Minor
- …
### Working well ✓
- …

**Top 3 priorities:** the highest-impact fixes for the target device.

End with the prioritized top 3 — that's what a calling generator acts on.

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How to run a good audit

1. Establish context — device class (phone/tablet/responsive web), the breakpoints in scope, orientation expectations, and the screen's primary task. Touch ergonomics can only be judged against the device and the action that matters most.
2. Confirm applicability — if it's genuinely desktop-only, skip rather than inventing findings.
3. Sweep all seven areas — the value over a default review is completeness; don't stop at touch-target size.
4. Use the thresholds — 44pt/48dp targets, ≥8dp spacing, ≥16px body, ~30–40 char lines — so findings are checkable, not vibes.
5. Defer contrast/AT/keyboard to accessibility, composition to aesthetics, flow to heuristics — don't re-derive them here.
6. Prioritize, don't enumerate — rate by whether it blocks the task on the device.

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Common do/don't patterns

| ❌ Don't | ✅ Do | |---|---| | "Make it responsive" / "buttons too small" | Name the principle + threshold (44pt/48dp, ≥16px) + the fix | | Treat every nit as equal | Rate by whether it blocks the task on the device; surface top 3 | | Shrink the desktop layout onto the phone | Reflow to a fluid single column; nothing exceeds viewport width | | Lock core features to one orientation | Essential actions work in portrait and landscape | | 28px targets with 2px gaps | ≥44pt/48dp targets, ≥8dp spacing, corners enlarged | | Primary CTA top-corner; delete in the thumb zone | Primary within thumb reach; destructive guarded / out of easy reach | | Full QWERTY for a phone-number field | Contextual keyboards; autofill; selection over typing | | Hide the only path to an action behind a swipe | Gestures supplement a visible control, never replace it | | Re-derive WCAG contrast or screen-reader issues | Defer to the accessibility audit | | Report only tap-target size | Sweep all seven areas; cite the principle and threshold |

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Source lessons (Uxcel)

• Responsive vs. Adaptive Design
• Designing Mobile Layout
• Designing for Mobile Interfaces
• Platform Adaptivity & Scaling
• Ensuring Mobile Accessibility
• Mobile-Specific Functions & Interactions

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Uxcel-Lab
• Source: Uxcel-Lab/product-skills
• License: MIT
• Homepage: https://uxcel.com

Install and usage instructions live in the source repository linked above.