excel-webview2-mcp

Excel WebView2 MCP

Professional MCP connectivity for Microsoft Excel add-ins running inside WebView2.

Important

As of v0.0.2, this server can launch Excel and sideload your add-in for you. You no longer need to start the dev server or attach a debugger before using it — excel_launch_addin will start your local dev server (if configured) and launch Excel with WebView2 remote debugging enabled on port 9222. Manual pre-launch is still supported: if an Excel add-in is already running with remote debugging on 9222, the server will attach to it.

What's New in v0.0.2

• Add-in lifecycle management — new tools launch and stop Excel add-ins directly from Claude Code:
  • excel_detect_addin — discover manifest and dev server configuration for the current project.
  • excel_launch_addin — start the dev server (if needed) and launch Excel with the add-in sideloaded and CDP port 9222 enabled.
  • excel_stop_addin — tear down the launched Excel session and dev server process tree.
• Read-only Excel inspection tools — a broad set of read operations for inspecting workbooks, worksheets, ranges, tables, pivots, charts, and more. None of these mutate workbook state:
  • Context & structure: excel_context_info, excel_workbook_info, excel_list_worksheets, excel_worksheet_info, excel_active_range, excel_used_range.
  • Range reads: excel_read_range, excel_range_properties, excel_range_formulas, excel_range_special_cells, excel_find_in_range.
  • Formatting & validation: excel_list_conditional_formats, excel_list_data_validations.
  • Tables & names: excel_list_tables, excel_table_info, excel_table_rows, excel_table_filters, excel_list_named_items.
  • Comments & shapes: excel_list_comments, excel_list_shapes.
  • Calculation & pivots: excel_calculation_state, excel_list_pivot_tables, excel_pivot_table_info, excel_pivot_table_values.
  • Charts: excel_list_charts, excel_chart_info, excel_chart_image.
  • Misc: excel_custom_xml_parts, excel_settings_get.
• Socket-based port detection replaces HTTP polling for more reliable dev-server and CDP readiness checks on Node 24.
• Robust cleanup on Windows — excel_stop_addin now force-kills the dev server process tree via taskkill.

Fork Notice

This repository is a fork of the Chrome DevTools MCP repository, ChromeDevTools/chrome-devtools-mcp. It preserves the upstream DevTools and MCP foundation, while adapting the connection model for Microsoft Excel add-ins hosted in WebView2.

What This Project Does

• Connects Claude Code to a locally running Excel add-in through the Chrome DevTools Protocol (CDP).
• Exposes MCP tools for inspection, automation, screenshots, console access, network inspection, and performance analysis.
• Targets the embedded WebView2 runtime used by Excel add-ins instead of a standalone Chrome session.

Connection Model

Claude Code
    |
    v
excel-webview2-mcp
    |
    v
WebView2 remote debugging endpoint (localhost:9222)
    |
    v
Locally running Excel add-in

That separation matters: excel-webview2-mcp is a bridge to an existing debug session. It is not the thing that launches or hosts the add-in.

Prerequisites

You have two supported workflows:

Auto-launch (recommended, v0.0.2+)

1. Your Office add-in project (with a manifest.xml and a dev server script) lives on disk.
2. Excel desktop is installed on Windows.
3. Node.js is installed and npx @dsbissett/excel-webview2-mcp@latest is runnable.

Call excel_detect_addin first to confirm the project is discovered, then excel_launch_addin to start the dev server and sideload the add-in into Excel with CDP port 9222 enabled. Use excel_stop_addin to tear everything down.

Manual / pre-attached

1. Your Excel add-in is already loaded and running in the local Excel desktop client.
2. WebView2 remote debugging is enabled and bound to port 9222 (see Launching Excel with the debug port).
3. The debugging endpoint is reachable at http://127.0.0.1:9222.

Verify with:

curl http://127.0.0.1:9222/json

Launching Excel with the debug port

This section applies to Excel desktop on Windows. Per Microsoft's WebView2 and Office add-in documentation, the supported way to pass Chromium flags into the WebView2 runtime is WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS. The WebView2 team also documents a registry-based fallback for persistent configuration.

If you are using Excel for Mac, this MCP server does not apply. Microsoft documents Excel for Mac debugging through Safari Web Inspector instead of a WebView2 CDP port.

Sources:

• WebView2 debug arguments and registry policy: https://learn.microsoft.com/en-us/microsoft-edge/webview2/how-to/debug-visual-studio-code
• Office add-ins debugging with Edge DevTools: https://learn.microsoft.com/en-us/office/dev/add-ins/testing/debug-add-ins-using-devtools-edge-chromium
• Office add-ins debugging overview, including Mac: https://learn.microsoft.com/en-us/office/dev/add-ins/testing/debug-add-ins-overview

Windows: preferred local-dev setup

Set the environment variable before launching Excel so the Excel process inherits it:

$env:WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS="--remote-debugging-port=9222"

Then:

1. Launch Excel from that same shell or from a parent process that inherited the variable.
2. Start your add-in locally.
3. Confirm the debug endpoint is live.

Worked example:

$env:WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS="--remote-debugging-port=9222"
start excel.exe

The Office add-ins team documents this environment-variable mechanism generically for WebView2-hosted add-ins, and the WebView2 team documents --remote-debugging-port=9222 as a valid browser argument.

Windows: persistent registry fallback

If you need a persistent machine-local setting, the WebView2 team documents this registry policy path:

HKEY_CURRENT_USER\Software\Policies\Microsoft\Edge\WebView2\AdditionalBrowserArguments

Use:

• Value name: EXCEL.EXE
• Value data: --remote-debugging-port=9222

Use the environment variable first for local development. It is easier to turn on and off and avoids leaving a persistent machine-wide setting behind.

Verify the endpoint

Run:

curl http://127.0.0.1:9222/json/version

A healthy response is JSON and includes fields such as:

{
  "Browser": "...",
  "Protocol-Version": "...",
  "webSocketDebuggerUrl": "ws://127.0.0.1:9222/devtools/browser/..."
}

If that curl command fails, Excel is not exposing the WebView2 debug port yet, and excel-webview2-mcp will not be able to attach.

Installation

The server ships as the npm package @dsbissett/excel-webview2-mcp and is invoked via npx. The configuration below is the same across every host — only the location of the config file changes.

Canonical MCP entry:

{
  "mcpServers": {
    "excel-webview2": {
      "command": "npx",
      "args": ["@dsbissett/excel-webview2-mcp@latest"]
    }
  }
}

claude mcp add excel-webview2 -- npx @dsbissett/excel-webview2-mcp@latest

[mcp_servers.excel-webview2]
command = "npx"
args = ["@dsbissett/excel-webview2-mcp@latest"]

Verifying the install

After adding the server, ask the model to call excel_detect_addin from your Office add-in project directory. A successful response confirms the MCP server is wired up; from there excel_launch_addin will take care of starting Excel.

By default, the server connects to the local WebView2 debugging endpoint at http://127.0.0.1:9222.

Local Development

npm install
npm run build
npm start

Supported Node.js versions are ^20.19.0, ^22.12.0, or >=23.