> ## Documentation Index
> Fetch the complete documentation index at: https://docs.postmetric.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Express.js

> Proxy PostMetric with Express.js

Proxy PostMetric through your Express.js application.

## Setup

### Step 1: Install dependencies

```bash theme={null}
npm install express http-proxy-middleware
```

### Step 2: Create proxy middleware

```javascript theme={null}
const express = require("express");
const { createProxyMiddleware } = require("http-proxy-middleware");

const app = express();

// Proxy tracking script
app.get(
  "/api/track.js",
  createProxyMiddleware({
    target: "https://your-postmetric-domain.com",
    changeOrigin: true,
    pathRewrite: {
      "^/api/track.js": "/api/track.js",
    },
    onProxyRes: function (proxyRes, req, res) {
      proxyRes.headers["content-type"] = "application/javascript";
    },
  })
);

// Proxy tracking endpoint
app.all(
  "/api/track",
  createProxyMiddleware({
    target: "https://your-postmetric-domain.com",
    changeOrigin: true,
    pathRewrite: {
      "^/api/track": "/api/track",
    },
  })
);

app.listen(3000);
```

### Step 3: Update tracking script URL

Update your tracking script to use your domain:

```html theme={null}
<script src="https://your-domain.com/api/track.js?site=YOUR_TRACKING_CODE"></script>
```

## Next steps

<Card title="Proxy setup guide" icon="shield" href="/proxy/get-started">
  Learn more about proxying PostMetric
</Card>