devtools

Use CDP at localhost:9222. For exploration, use tmux with websocat, or wscat, or uv run --with playwright,markdownify,httpx,readability python -m asyncio (starts Python REPL with top-level await). For automation, npm install playwright and code in node.

Capabilities:

• For DOM HTML to Markdown: turndown, markdownify, or uvx markitdown file.html
• Log progress via console: page.on("console", msg => console.log("LOG:", msg.type(), msg.text())). Use CDP's Console.enable for replay
• Log screenshots via (page||locator).screenshot({ path, fullPage, type, quality, ... })
• Intercept fetch/XHR, parse JSON directly, cache for repeat runs
• HAR traces: context.tracing.start({ screenshots: true, snapshots: true }) ... context.tracing.stop({ path: "trace.zip" })
• Inject JS into existing tabs via a blob: URL created in the page context. CSP may block inline scripts.
  • url = URL.createObjectURL(new Blob([code], { type: "text/javascript" }))
  • Append <script src="blob:...">
  • Avoid page.addScriptTag({content: ...}) on CSP-heavy sites (e.g. WhatsApp, Google apps).

Uses: