How to Fix Proxy Error in React

The proxy error in React can be frustrating, especially when it appears without an obvious cause. Let's break down exactly what's happening and how to resolve it quickly.

Why It Happens

Proxy errors in React arise when a request can't reach its destination through an intermediary server. Typical causes include:

• Misconfigured proxy URL, port, or protocol
• The proxy server is down, overloaded, or unreachable
• Timeout settings are too aggressive for the proxy's latency
• SSL/TLS certificate issues when proxying HTTPS traffic
• DNS resolution failures within the proxy network

Fixing the Issue

// next.config.js — proxy API calls to backend
module.exports = {
  async rewrites() {
    return [
      {
        source: "/api/:path*",
        destination: "http://backend:3001/api/:path*",
      },
    ];
  },
  // For development proxy with custom timeout
  serverRuntimeConfig: {
    apiTimeout: 30000,
  },
};

// In your API route, handle proxy failures
export async function handler(req, res) {
  try {
    const response = await fetch("http://backend:3001" + req.url);
    const data = await response.json();
    res.json(data);
  } catch (err) {
    console.error("Backend proxy failed:", err.message);
    res.status(502).json({ error: "Service unavailable" });
  }
}

Configure Next.js rewrites for proxying and add error handling in API routes for when the backend is unreachable.

Debugging Steps

1. Verify the proxy server is reachable: curl -x proxy:port https://target
2. Check environment variables: HTTP_PROXY, HTTPS_PROXY, NO_PROXY
3. Ensure DNS resolution works within your network environment
4. Review firewall rules between your app and the proxy server
5. Test with increased timeouts to rule out latency issues

Monitor proxy failures across all your services with [Bugsly](https://bugsly.dev) to spot network infrastructure issues before they cascade into outages.