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21st-ui-review — Claude Code skill: UI audit and fixes

Reviews existing UI for accessibility, responsive behavior and drift from the project's design system. Useful before shipping a page or after someone else's pull request.

Install into Claude Code · Skills CLI (Vercel) All methods and platforms ↓
npx skills add 21st-dev/skill --skill 21st-ui-review -a claude-code
Open on GitHub

What 21st-ui-review does

The skill separates deterministic defects from taste. It reads .21st/design.json, project instructions and the relevant source, then runs 21st review <path>, plain or with --json. From there it inspects the actual component composition and runtime states instead of guessing from names.

Findings land in groups: deterministic defects, design-system drift, accessibility and interaction problems, responsive risks, and subjective recommendations. Each one carries a file and line. Fixes go through 21st review <path> --fix, and only for low-ambiguity cases. It will not quietly redesign a screen or change product behavior.

Priorities cover semantic controls and accessible names, keyboard access and focus visibility, touch target size, loading and disabled states, overflow on narrow screens, prefers-reduced-motion, and hardcoded values that fight project tokens. After a fix the skill suggests running the project tests and rerunning the review to prove the defect is gone.

What it helps with

  • catch accessibility defects on a page before release
  • spot layout overflow on narrow viewports
  • check colors and spacing against design tokens
  • verify dialogs and menus work from the keyboard
  • separate real defects from nitpicks in a frontend review

Example prompts for the agent

  • review this UI for accessibility and responsive issues
  • audit the checkout page and list findings by file
  • find obvious UX problems in the cart component

How to install 21st-ui-review

1Skills CLI (Vercel)

npx skills add 21st-dev/skill --skill 21st-ui-review -a claude-code

2Manually: put the files in place

~/.claude/skills/21st-ui-review/SKILL.md

Copy the whole skill folder; for one project use .claude/skills/21st-ui-review/

Step by step, with commands for each platform: How to install skills in Claude Code: five ways

Questions about 21st-ui-review

How do I install 21st-ui-review in Claude?

Run npx skills add 21st-dev/skill --skill 21st-ui-review -a claude-code. The skill lands in ~/.claude/skills/21st-ui-review/SKILL.md.

What does 21st-ui-review do?

It reviews existing UI for deterministic defects, design-system drift, accessibility and responsive problems. Subjective suggestions are labeled separately.

How is 21st-ui-review different from 21st-ui-build?

This skill reviews UI that already exists. When the task is to create new UI, use 21st-ui-build.

Source text

SKILL.md · Apache-2.0
---
name: 21st-ui-review
description: Review existing UI against the project's design context, accessibility expectations, responsive behavior, interaction quality, and high-confidence production rules. Use for UI audits, design QA, frontend review, accessibility review, consistency checks, or requests to find and safely fix visual defects. Trigger for requests such as "review this UI", "audit this page", "find design issues", "check responsiveness", or "fix obvious UX problems". Use 21st-ui-build when the request is primarily to create new UI.
---

# Review UI with evidence

Separate deterministic defects from subjective design recommendations.

## Workflow

1. Read `.21st/design.json`, project instructions, and the relevant source.
2. Run the deterministic review first:

   ```bash
   21st review <path>
   21st review <path> --json
   ```

3. Inspect the actual component composition and runtime states. Validate claims
   against code rather than inferring behavior from names.
4. Group findings into:
   - deterministic defects;
   - design-system drift;
   - accessibility and interaction defects;
   - responsive risks;
   - subjective product/design recommendations.
5. Prioritize by user impact and include exact file and line attribution.
6. Use `21st review <path> --fix` only for deterministic, low-ambiguity fixes.
   Never silently redesign, change brand identity, or alter product behavior.
7. Run relevant project tests after fixes and rerun review to prove resolution.

## Review priorities

- semantic controls and accessible names;
- keyboard access, focus visibility, and dialog/menu behavior;
- image alternatives and meaningful labels;
- touch target size and disabled/loading states;
- responsive overflow and fixed-width assumptions;
- reduced-motion handling;
- hardcoded visual values that conflict with project tokens;
- duplicate primitives instead of existing components;
- inconsistent typography, radius, spacing, shadows, and icons;
- fake data, placeholder copy, or missing empty/error states.

## Output

Lead with actionable findings ordered by severity. Keep subjective suggestions
clearly labeled. If no issue is proven, say so and state what was inspected.

© 21st-dev · Apache-2.0 · 21st-dev/skill

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