localhost-screenshots（本地主机截图）

Localhost Screenshots

Installation

npx skills add t4sh/skills4sh --skill localhost-screenshots

This skill captures screenshots of locally running websites. It supports two primary approaches depending on the task:

• Chrome MCP — for quick debugging, single screenshots, and interactive verification
• Playwright — for systematic multi-breakpoint screenshot sets and visual regression

For niche scenarios (CDP attach, persistent sessions, AI snapshots, CI workflows), see the Reference Files section.

Tool Decision Matrix — Read This First

Chrome MCP — Quick Screenshots & Debugging

Use a Chrome-connected MCP for one or two screenshots or interactive debugging. It drives the user’s real browser, which can already reach their localhost dev server. No Playwright install required.

MCP tool names (map to the host's server)

Identifiers differ by host. Map capabilities to the host server's actual tools:

Follow the MCP server's lock/snapshot rules (e.g. Cursor: snapshot before structural changes).

Prerequisites

The user's dev server must be running (e.g., npx @11ty/eleventy --serve --port=3000).

Quick screenshot flow (pattern)

1. Ensure a browser tab (create if empty).
2. Navigate to http://localhost:<port>/<path>.
3. Take a viewport screenshot.
4. Optionally resize, then screenshot again.

Example: Claude Chrome MCP

mcp__Claude_in_Chrome__tabs_context_mcp({ createIfEmpty: true })
mcp__Claude_in_Chrome__navigate({ url: "http://localhost:3000/dashboard/" })
mcp__Claude_in_Chrome__computer({ action: "screenshot" })
mcp__Claude_in_Chrome__resize_window({ width: 375, height: 812 })
mcp__Claude_in_Chrome__computer({ action: "screenshot" })

Example: Cursor IDE browser

Navigate with browser_navigate, then browser_take_screenshot. Use browser_snapshot before interactions; follow cursor-ide-browser server instructions for lock/unlock if required.

Debugging patterns (run JS in page)

Payload examples (wrap in the MCP's JS action):

JSON.stringify(Object.keys(window.MyApp || {}))

JSON.stringify(getComputedStyle(document.querySelector('.target')).background)

JSON.stringify(document.querySelector('.target').getBoundingClientRect())

JSON.stringify({ title: document.title, url: location.href, stylesheets: document.querySelectorAll('link[rel=stylesheet]').length })

Claude Chrome MCP shape:

mcp__Claude_in_Chrome__javascript_tool({
  action: "javascript_exec",
  text: "<escaped one-line string>"
})

When NOT to Use Chrome MCP for Screenshots

• When all 8 breakpoints need capture systematically — use Playwright
• When repeatable, scriptable visual regression is required — use Playwright
• When generating a before/after comparison HTML — use Playwright

Playwright — Systematic Multi-Breakpoint Screenshots

Use Playwright for automated, repeatable screenshot sets across all breakpoints. This is the right tool for visual regression testing and comprehensive responsive documentation.

Golden Rules

1. Always use Playwright’s bundled Chromium. Never use Puppeteer, Selenium, or system Chrome. Do not check for installed browsers.
2. Prefer HTTP; file:// only for self-contained static HTML. Serve over HTTP whenever a dev server, build output, or npx serve is available. file:// is acceptable *only* when the page has no fetch/XHR to sibling files, no <script type="module">, no service workers, and no absolute /asset paths — otherwise those will break silently. When in doubt, serve over HTTP.

Setup (run once per session)

node -e “require(‘playwright’)” 2>/dev/null || npm install playwright 2>/dev/null
npx playwright install --with-deps chromium

Do not use @latest — let the project’s lockfile control the version.

Quick workflow

1. Ensure the site is served over HTTP (user’s dev server, or npx serve _site -l 3000 &).
2. Verify the server responds before screenshotting (see playwright-patterns.md § “Verifying the Server”).
3. Capture all 8 standard breakpoints (320–1920px) unless the user asks for specific sizes. Check the project’s CSS/Tailwind config for custom breakpoints first.
4. Save to _screenshots/ in the project folder.

For the canonical screenshot script, standard breakpoints array, serving patterns, server verification, waiting for dynamic content, element screenshots, persistent sessions, and when the dev server isn’t running — see references/playwright-patterns.md.

Output structure

_screenshots/
  home/
    mobile-sm-320x568.png
    mobile-375x812.png
    ...
    wide-1920x1080.png
  about/
    ...

Before/after visual comparison

Run the canonical script twice (_screenshots/before, _screenshots/after), then generate a comparison HTML. For the comparison script and pixel-diff scoring, see references/visual-regression.md.

Key API notes

• chromium.launch() — no arguments, uses Playwright’s bundled Chromium
• waitUntil: ‘networkidle’ — good for static sites. SPAs with analytics/websockets may never go idle — use load + waitForSelector instead
• fullPage: true — captures entire scrollable page
• Create a new page per breakpoint — avoids leftover state
• page.setViewportSize() — set before navigating for accurate responsive rendering

What NOT to Do

See references/troubleshooting.md § "What NOT to Do" for the full list. Key items: no Puppeteer, no JSDOM, no system Chrome binaries, no file:// paths, always capture all breakpoints.

Related Skills

Built-in (Claude Code):

• dev-browser — browser automation with persistent page state. Useful for interactive captures and manual navigation before screenshotting

On skills.sh:

• screenshot-local — shot-scraper (Playwright-based) for localhost captures with custom viewports, element targeting, and batch YAML configs. Lighter-weight alternative when a full regression pipeline isn't needed
• visual-regression-tester — automated visual regression via Playwright, Chromatic, or Percy with multi-viewport and CI/CD. Complements the pixel-diff reference in this skill
• playwright-responsive-screenshots — MCP-only responsive captures at 3 breakpoints (mobile/tablet/desktop). Lighter scope; localhost-screenshots is a superset: two tracks (Chrome MCP for debug + Playwright for regression), 8 breakpoints with Tailwind/media-query detection, guided Playwright setup, in-page JS debugging, pre-flight checks, persistent sessions, visual-regression pipeline with pixel-diff, and framework-specific troubleshooting

Reference Files

For advanced patterns (CDP attach, persistent sessions, pixel-diff, AI snapshots, CI workflows), read these files from the references/ directory: