React + Express: The Frustrating Mystery of Mixed Content Errors

Have you ever encountered the infuriating error message “The page at [your domain] was loaded over HTTPS, but requested an insecure resource” while building a React application with an Express backend? You’re not alone! This pesky issue has plagued many developers, and today, we’re going to tackle it head-on.

What is Mixed Content, Anyway?

Mixed content occurs when a web page loaded over HTTPS (the secure protocol) requests resources, such as images, scripts, or stylesheets, over HTTP (the insecure protocol). This creates a security vulnerability, as an attacker could intercept and manipulate the insecure resources, compromising the entire page. Modern browsers, in their quest for security, will block these requests to prevent such attacks.

The React + Express Conundrum

In a typical React + Express setup, your Express server runs on a different port than your React application. When you make requests from your React app to the Express server, the protocol used is HTTP by default. However, if your React app is served over HTTPS, you’ve got a mixed content problem on your hands!

The Culprits: Identifying Insecure Requests

To fix the issue, you need to identify which resources are being requested over HTTP. Here are some common culprits:

• API calls to your Express server from your React app
• Image or file requests from your React app to your Express server
• CDN-hosted scripts or stylesheets loaded in your React app
• Third-party libraries or services that use HTTP

Solution 1: Enable HTTPS for Your Express Server

The most straightforward solution is to enable HTTPS for your Express server. This way, all requests from your React app to the Express server will be secure.

const express = require('express');
const https = require('https');
const fs = require('fs');

const app = express();

const sslOptions = {
  key: fs.readFileSync('path/to/your/key.pem'),
  cert: fs.readFileSync('path/to/your/cert.pem')
};

https.createServer(sslOptions, app).listen(3001, () => {
  console.log('Express server listening on port 3001 with HTTPS');
});

In this example, we’re using the `https` module to create an HTTPS server with a self-signed certificate (replace with your own certificate files). Make sure to update your React app to make requests to `https://localhost:3001` instead of `http://localhost:3001`.

Solution 2: Use a Reverse Proxy with NGINX or Apache

If enabling HTTPS for your Express server isn’t feasible, you can set up a reverse proxy using NGINX or Apache. This will allow you to serve your React app over HTTPS while proxying requests to your Express server over HTTP.

NGINX Configuration

server {
  listen 443 ssl;
  server_name example.com;

  ssl_certificate path/to/your/cert.pem;
  ssl_certificate_key path/to/your/key.pem;

  location /api {
    proxy_pass http://localhost:3001;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection 'upgrade';
    proxy_set_header Host $host;
    proxy_cache_bypass $http_upgrade;
  }
}

Apache Configuration

<VirtualHost *:443>
  ServerName example.com
  SSLEngine on
  SSLCertificateFile path/to/your/cert.pem
  SSLCertificateKeyFile path/to/your/key.pem

  <Proxy *>
    Order allow,deny
    Allow from all
  </Proxy>

  ProxyPass /api http://localhost:3001
  ProxyPassReverse /api http://localhost:3001
</VirtualHost>

In both configurations, we’re setting up a reverse proxy to forward requests from `https://example.com/api` to `http://localhost:3001`. Update your React app to make requests to `https://example.com/api` instead of `http://localhost:3001`.

Solution 3: Update Insecure Requests to HTTPS

If you can’t or won’t enable HTTPS for your Express server, you can update individual requests in your React app to use HTTPS.

import axios from 'axios';

axios.create({
  baseURL: 'https://localhost:3001/api'
});

// or

fetch('https://localhost:3001/api/data', {
  method: 'GET',
  headers: {
    'Content-Type': 'application/json'
  }
})
.then(response => response.json())
.catch(error => console.error(error));

In this example, we’re updating Axios to use HTTPS for all requests to `https://localhost:3001/api`. You can apply this approach to individual requests or libraries that use HTTP.

Solution 4: Use a CORS Proxy

If you’re dealing with third-party libraries or services that use HTTP, you can set up a CORS proxy to forward requests from HTTP to HTTPS.

const express = require('express');
const cors = require('cors');
const proxy = require('proxy-middleware');

const app = express();

app.use(cors());

app.use('/proxy', proxy('https://third-party.com'));

app.listen(3002, () => {
  console.log('CORS proxy listening on port 3002');
});

In this example, we’re setting up a CORS proxy using Express and the `proxy-middleware` library. The proxy forwards requests from `http://localhost:3002/proxy` to `https://third-party.com`. Update your React app to make requests to `http://localhost:3002/proxy` instead of `http://third-party.com`.

Conclusion

Mixed content errors can be frustrating, but with these solutions, you should be able to resolve the issue and ensure a secure connection between your React app and Express server. Remember to enable HTTPS for your Express server, set up a reverse proxy, update insecure requests, or use a CORS proxy depending on your specific situation.

By following these steps, you’ll be saying goodbye to the “The page at [your domain] was loaded over HTTPS, but requested an insecure resource” error and hello to a more secure and reliable application!

Solution	Description
Enable HTTPS for Express Server	Configure Express server to use HTTPS
Use a Reverse Proxy with NGINX or Apache	Proxy requests from HTTPS to HTTP using NGINX or Apache
Update Insecure Requests to HTTPS	Update individual requests in React app to use HTTPS
Use a CORS Proxy	Forward requests from HTTP to HTTPS using a CORS proxy

Choose the solution that best fits your needs, and don’t hesitate to experiment with different approaches until you find the one that works for you.

Here are the 5 Questions and Answers about “React + Express: Mixed Content The page at was loaded over HTTPS but requested an insecure resource”

Frequently Asked Question

Mixed content errors can be frustrating! But don’t worry, we’ve got you covered. Here are some FAQs to help you troubleshoot and resolve the “The page at was loaded over HTTPS but requested an insecure resource” error in your React + Express application.