Proxy DataFast with Firebase Hosting

Learn how to proxy DataFast analytics through Firebase Hosting using Cloud Functions to bypass adblockers and improve accuracy.

Note: Firebase Hosting does not support reverse proxy and rewrite rules for external destinations natively. This guide uses Firebase Cloud Functions as a workaround.

1. Set up Firebase Functions (if not already done)

If you haven't yet, add support of Firebase Functions to your Firebase project:

firebase init functions

Follow the instructions according to your setup. At the end, you should have a /functions folder in your project.

2. Install Dependencies

Make sure you're in the functions/ folder and install required dependencies:

cd functions/
npm i -s express express-http-proxy

3. Create ReverseProxy Firebase Function

Create or update your functions/index.js file with the following code:

const { onRequest } = require("firebase-functions/v2/https");
const express = require("express");
const proxy = require("express-http-proxy");

const app = express();

app.set("trust proxy", true);

// Proxy the DataFast script
app.use(
  "/js/script.js", proxy("https://datafa.st", {
    proxyReqPathResolver: () => "/js/script.js",
  }),
);

// Proxy the events endpoint
app.use(
  "/api/events", proxy("https://datafa.st", {
    proxyReqPathResolver: () => "/api/events",
  }),
);

exports.reverseProxy = onRequest(app);

4. Configure Firebase Hosting Rewrites

Update your firebase.json to point to the reverseProxy function:

{
  "hosting": {
    "public": "public",
    "ignore": [
      "firebase.json",
      "**/.*",
      "**/node_modules/**"
    ],
    "rewrites": [
      {
        "source": "/js/script.js",
        "function": "reverseProxy"
      },
      {
        "source": "/api/events",
        "function": "reverseProxy"
      }
    ]
  },
  "functions": [
    {
      "source": "functions",
      "codebase": "default",
      "ignore": ["node_modules", ".git", "firebase-debug.log", "firebase-debug.*.log", "*.local"]
    }
  ]
}

5. Update Your Script Tag

Replace your existing DataFast script with the proxied version:

<script
  defer
  data-website-id="yourwebsiteid"
  data-domain="yourdomain.com"
  src="/js/script.js"
></script>

6. Deploy Firebase Hosting and Functions

Deploy both hosting and functions:

firebase deploy --only hosting,functions

Verification

To verify the proxy is working:

Visit your website
Open the network tab in your browser's developer tools
Check that analytics requests are going through your domain instead of datafa.st

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