No Extensions Allowed: The Chrome DevTools MCP Dilemma

The Problem Blocking Developers from AI-Powered Debugging

Chrome DevTools MCP is a game-changer for AI coding assistants. It gives tools like GitHub Copilot and Cursor the ability to see what your code actually does in the browser—debugging console errors, analyzing DOM structure, capturing screenshots, and validating UI alignment in real-time.

It's like giving your AI assistant eyes.

But there's a critical limitation that's been blocking developers from using this powerful capability: authentication.

Here's what happens: When you use Chrome DevTools MCP with tools like GitHub Copilot or Cursor, it spawns a Chrome browser instance that doesn't allow extension installation. This means there's no way to attach cookie headers or authentication tokens when connecting to staging APIs from your locally running frontend.

The result? You can't use Chrome DevTools MCP to debug authenticated applications. No staging environment testing. No real user session debugging. The very scenarios where AI-assisted debugging would be most valuable become impossible.

Why This Matters for Modern Development

Chrome DevTools MCP brings incredible capabilities to AI coding assistants. According to Google's announcement, it enables AI agents to:

• Verify code changes in real-time by actually running them in the browser
• Diagnose network and console errors by inspecting live requests and logs
• Simulate user behavior to reproduce bugs and test complex flows
• Debug styling and layout issues with access to live DOM and CSS data
• Automate performance audits with Chrome's powerful profiling tools

But here's the catch: most real-world applications require authentication. Whether you're:

• Testing API integrations against staging environments
• Debugging authentication flows in local development
• Working with cookie-based session management
• Dealing with protected endpoints that require bearer tokens

…the spawned Chrome instance can't authenticate, and Chrome DevTools MCP becomes useless for your actual workflow.

The Solution: A Lightweight Authentication Proxy

I built a simple Express-based proxy server that elegantly solves this authentication gap. Instead of trying to inject credentials into the spawned Chrome instance (impossible without extensions), we route API calls through a local proxy that automatically attaches authentication credentials.

The approach is straightforward: Your frontend running in the Chrome DevTools MCP browser points to a local proxy. The proxy forwards requests to your staging API while seamlessly injecting cookies, bearer tokens, or any custom headers you need.

How It Works in Practice

1. Clone and install:

git clone https://github.com/vsanse/proxy-node cd proxy-node npm install

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1. Configure your authentication:

cp .env.example .env

Edit .env with your API and credentials:

TARGET_API=https://your-staging-api.com COOKIE_STRING=your_full_cookie_string_here # Optional: Add custom headers as JSON CUSTOM_HEADERS={"Authorization": "Bearer token123", "X-Custom-Header": "value"}

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1. Start the proxy:

npm start # Or for development with auto-reload npm run dev

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1. Update your frontend configuration: Instead of calling https://your-staging-api.com/endpoint directly, point to http://localhost:3001/endpoint. The proxy handles authentication transparently.

Unlocking AI-Assisted Debugging for Authenticated Apps

With this proxy in place, you can now leverage the full power of Chrome DevTools MCP with your AI coding assistant on authenticated applications:

Real-World Scenario 1: Debugging API Errors with AI

Prompt for your AI assistant: "The user dashboard isn't loading. What's happening?"

Your AI can now:

• Connect to your local dev server via Chrome DevTools MCP
• See the actual 401 errors in the console (now properly authenticated through the proxy)
• Analyze network requests to your staging API
• Identify the root cause and suggest fixes

Real-World Scenario 2: Visual Regression Testing

Prompt: "Check if the navigation menu looks correct after my recent changes."

Your AI can:

• Take screenshots of your authenticated app
• Compare DOM structure against expected layout
• Spot visual regressions in protected routes
• Suggest CSS fixes based on live browser data

Real-World Scenario 3: Performance Optimization

Prompt: "The authenticated user feed is loading slowly. Investigate and fix it."

Your AI can:

• Run performance traces on authenticated routes
• Analyze API response times through the proxy
• Identify bottlenecks in data fetching
• Recommend optimizations based on real metrics

Why This Approach Works

Transparent to your app: No code changes needed in your frontend. Just update the API endpoint configuration.

Flexible authentication: Works with cookies, bearer tokens, custom headers—whatever your staging environment requires.

Zero Chrome modifications: We work around the extension limitation rather than fighting it.

AI-friendly: Your coding assistant sees real authenticated responses, making its suggestions dramatically more accurate.

Team-ready: Share the proxy config (minus credentials) with your team for consistent local development.

Beyond the Original Problem

While I built this specifically for Chrome DevTools MCP authentication, the proxy is valuable for any scenario where you need to:

• Test authenticated staging APIs locally
• Debug session-based authentication flows
• Work around CORS restrictions during development
• Switch between multiple environments quickly

Getting Started

The repository is open source and takes less than 5 minutes to set up:

GitHub: https://github.com/vsanse/proxy-node

Once running, you can finally use Chrome DevTools MCP with tools like GitHub Copilot or Cursor on your real, authenticated applications. Your AI assistant can see what your code actually does in the browser, analyze console errors with full context, and provide accurate debugging suggestions based on live data.

What's Next?

I'm actively maintaining this project and exploring enhancements like:

• Support for multiple target APIs simultaneously
• Request/response logging for debugging
• OAuth flow helpers
• Configuration UI for easier setup

The Bottom Line

Chrome DevTools MCP is a powerful capability that dramatically improves AI coding assistant accuracy by giving them visibility into what your code actually does in the browser. But without authentication, it's been unusable for real-world applications.

This proxy removes that barrier entirely.

No more manual token copying. No more skipping AI-assisted debugging on authenticated features. No more wondering if your staging environment is causing issues.

Just clone, configure, and unlock the full potential of AI-powered debugging with Chrome DevTools MCP.

Try it out: https://github.com/vsanse/proxy-node

Found this helpful? Star the repo and share it with developers using GitHub Copilot, Cursor, or other AI coding assistants with MCP support.

Want to contribute? PRs are welcome! Let's make AI-assisted debugging work seamlessly for authenticated applications.

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