Fix AuthenticationError Error in Gatsby — In Production

What Is the AuthenticationError Error?

Let's tackle the AuthenticationError error that Gatsby developers frequently encounter. The fix is simpler than you might think.

Why It Happens

This typically means the authentication layer is rejecting requests — often due to expired tokens, missing API keys, or incorrect auth configuration. In production, this is often triggered by environment differences between local and deployed setups.

The Fix

const token = process.env.AUTH_TOKEN;
if (!token) throw new Error('AUTH_TOKEN not set');

const res = await fetch('/api/protected', {
  headers: { Authorization: `Bearer ${token}` }
});
if (res.status === 401) {
  // Token expired — refresh it
}

Additional Context

The AuthenticationError error in Gatsby is particularly common in applications that handle asynchronous operations or external service integrations. As your application scales, this error may appear more frequently due to increased concurrent requests or resource contention. Implementing proper error boundaries, health checks, and circuit breakers can significantly reduce the impact when this error occurs. Regular load testing helps identify these issues before they affect real users.

Prevention

Use [Bugsly](https://bugsly.dev) to monitor your app and capture errors like this automatically with actionable context.

Key Takeaways

• Always handle this error gracefully with proper error handling
• Check your environment configuration — especially in production
• Test thoroughly before deploying to production