# WebPerf Snippets (MCP server)

> WebPerf Snippets is an MCP server that runs curated WebPerf Snippets headlessly via Playwright. Diagnose Core Web Vitals beyond what Lighthouse exposes and gate CI on real performance budgets. It has 1,454 GitHub stars, is released under the MIT license and runs locally with npx -y webperf-snippets.

Run curated WebPerf Snippets headlessly via Playwright. Diagnose Core Web Vitals beyond what Lighthouse exposes and gate CI on real performance budgets.

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/nucliweb/webperf-snippets |
| GitHub stars | 1,454 |
| License | MIT |
| Language | JavaScript |
| Transport | stdio |
| Packages | npm: webperf-snippets |
| Remote URL | none |
| Needs API key | yes |
| Official | no |
| Works with | Claude Desktop, Claude Code, Cursor, VS Code |
| Category | Web & browsing |
| Latest release | v2.1.0 (Oct 25, 2026) |
| Last commit | Oct 26, 2026 |
| MCP registry name | io.github.nucliweb/webperf-snippets |

## Install

### Claude Desktop (claude_desktop_config.json)

```json
{
  "mcpServers": {
    "webperf-snippets": {
      "command": "npx",
      "args": [
        "-y",
        "webperf-snippets"
      ],
      "env": {
        "CRUX_API_KEY": "your-value"
      }
    }
  }
}
```

Settings > Developer > Edit Config. macOS: ~/Library/Application Support/Claude/, Windows: %APPDATA%\Claude\. Restart Claude Desktop afterwards.

### Claude Code

```sh
claude mcp add --env CRUX_API_KEY=your-value --transport stdio webperf-snippets -- npx -y webperf-snippets
```

### Cursor (.cursor/mcp.json)

```json
{
  "mcpServers": {
    "webperf-snippets": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "webperf-snippets"
      ],
      "env": {
        "CRUX_API_KEY": "your-value"
      }
    }
  }
}
```

Project file; use ~/.cursor/mcp.json to enable it in every project.

### VS Code (.vscode/mcp.json)

```json
{
  "inputs": [
    {
      "type": "promptString",
      "id": "crux_api_key",
      "description": "CRUX_API_KEY",
      "password": true
    }
  ],
  "servers": {
    "webperf-snippets": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "webperf-snippets"
      ],
      "env": {
        "CRUX_API_KEY": "${input:crux_api_key}"
      }
    }
  }
}
```

Config formats checked against the official docs on 2026-10-07.

## Environment variables

- `CRUX_API_KEY` (secret): Chrome UX Report API key for the field data of get_crux; the other tools work without it

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---

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