Resizes a browser window through 8 standard breakpoints (or every 160px in sweep mode) and screenshots each width to catch layout breaks. The real value is in transition detection: it tells you exactly where your navigation switches to hamburger, where columns reflow, where overflow starts. Checks the eight things that actually vary by viewport (overflow, text truncation, touch target size, CTA visibility) and skips general accessibility stuff that doesn't change with width. Works with playwright-cli, Playwright MCP, or Chrome MCP. Good for debugging that mysterious tablet-range jank or confirming your CSS breakpoints match actual layout shifts.
npx skills add https://github.com/jezweb/claude-skills --skill responsiveness-check