/chrome-devtools-mcp

name: chrome-devtools-mcp
description: "Use Chrome DevTools MCP from .NET agents and .NET-focused repos to inspect, debug, and automate Chrome through an MCP client. USE FOR: the repo needs browser-level debugging for ASP.NET Core, Blazor, WebAssembly, or any .NET app with a web UI; the user wants an MCP server that can inspect console. DO NOT USE FOR: pure .NET code analysis, unit testing, or NuGet/package management; static HTML linting alone. INVOKES: inspect the repository context, edit targeted files, and run relevant build, test, lint, or validation commands when changes are made."
compatibility: "Requires an MCP-capable .NET agent/app or repo with a browser-debugging workflow; Chrome DevTools MCP runs as an external Node-based server and needs Chrome or Chrome for Testing."

Chrome DevTools MCP for .NET Repos

Trigger On

• the repo needs browser-level debugging for ASP.NET Core, Blazor, WebAssembly, or any .NET app with a web UI
• the user wants an MCP server that can inspect console output, network traffic, screenshots, traces, and DOM state
• the repo needs agent-friendly browser control instead of manual DevTools work

Do Not Use For

• pure .NET code analysis, unit testing, or NuGet/package management
• static HTML linting alone
• sensitive browser sessions that must not be exposed to an MCP client

Inputs

• the nearest `AGENTS.md`
• the MCP client config for the current agent or app
• the target Chrome mode: launch new, connect to existing browser, or attach to a WebSocket endpoint
• the target app URL or local dev server

Workflow

1. Choose the browser mode first.

• new ephemeral browser: default when you want a clean session
• existing browser: use `--browserUrl` or `--wsEndpoint`
• running browser with a user profile: use `--autoConnect` only when Chrome 144+ and remote debugging are already enabled

2. Prefer repo-local config over ad hoc shell commands.

• store the MCP server block in the repo or agent config so every run is repeatable

3. Start from the smallest useful surface.

• use `--slim` when you only need navigation, JavaScript execution, and screenshots
• leave the full toolset enabled when you need network, performance, or emulation

4. Be explicit about privacy and cost.

• disable usage statistics or CrUX-backed performance enrichment when policy or sensitivity requires it

5. Validate against the real app, not a mock page.

• use the app's local dev server, preview URL, or a production-like environment that reflects the bug

Current Upstream Notes

• Chrome DevTools MCP `v1.6.0` adds heap-snapshot aggregate filters and object-count/total-size details, `--allow-unrestricted-paths`, experimental GCF-encoded responses, and Lighthouse 13.4.0.
• The same release fixes page-id reuse across reconnects, snapshot element resolution, first-page pagination, selected-page fallback behavior, held modifier cleanup, and daemon startup races. Reproduce browser-state bugs after upgrading before adding client-side retries or page-id workarounds.
• Use the memory tools only when heap snapshots are the actual debugging need; close snapshots when finished so the browser session does not keep unnecessary memory pressure.
• For sensitive or scoped browser automation, prefer `allowedUrlPattern` / `blockedUrlPattern` over relying only on prompt instructions.
• When enabling category extensions, prompt the user for the category instead of silently broadening the tool surface.

Install And Configure

Use the same JSON MCP server block in whatever .NET agent/app host you use:

{
  "mcpServers": {
    "chrome-devtools": {
      "command": "npx",
      "args": ["-y", "chrome-devtools-mcp@latest"]
    }
  }
}

Common variants:

{
  "mcpServers": {
    "chrome-devtools": {
      "command": "npx",
      "args": ["-y", "chrome-devtools-mcp@latest", "--slim", "--headless"]
    }
  }
}

{
  "mcpServers": {
    "chrome-devtools": {
      "command": "npx",
      "args": ["-y", "chrome-devtools-mcp@latest", "--browserUrl", "http://127.0.0.1:9222"]
    }
  }
}

For Codex CLI, the upstream repo documents:

codex mcp add chrome-devtools -- npx chrome-devtools-mcp@latest

Useful Flags

• `--slim`: three-tool surface for navigation, JavaScript execution, and screenshots only
• `--headless`: run without UI
• `--browserUrl` or `--wsEndpoint`: attach to an existing debuggable browser
• `--wsHeaders`: add custom WebSocket headers when `--wsEndpoint` is used
• `--autoConnect`: connect to a locally running Chrome 144+ instance instead of launching a new one
• `--channel stable|beta|dev|canary`: pick a Chrome channel
• `--isolated`: create and clean up a temporary profile
• `--userDataDir`: reuse a specific Chrome profile directory
• `--no-usage-statistics`: opt out of usage collection
• `--no-performance-crux`: stop sending performance trace URLs to CrUX
• `--acceptInsecureCerts`: only when the target environment uses self-signed or expired certs
• `--allow-unrestricted-paths`: opt out of filesystem path restrictions only for a trusted local workflow that genuinely needs arbitrary path access
• `--logFile <path>`: capture debug logs for bug reports
• `--experimentalScreencast`: only when ffmpeg is available and you need video capture

Practical Usage Patterns

• Debug a local ASP.NET Core or Blazor app:
• start the app
• connect with `--browserUrl` if the browser is already running, or let the server launch Chrome
• ask the agent to inspect console errors, network failures, and rendering behavior
• Investigate a flaky UI test:
• use `--headless --isolated`
• capture screenshots and console logs from the failing route
• compare the result to a known-good run
• Diagnose performance regressions:
• keep the full toolset enabled
• use performance tools only when you need trace data
• prefer `--slim` for quick smoke checks, not for performance work
• Work in a sandboxed or containerized environ