How to Fix CSRF Error in Astro

Dealing with a CSRF Error in your Astro project? You're in the right place. Let's solve this step by step.

What Causes This Error

CSRF errors happen when your application can't verify that a form submission originated from your own site. Without proper token validation, the server rejects the request to prevent malicious cross-site attacks.

The Fix

The key is to validate CSRF tokens in Astro middleware by comparing header to cookie value:

// src/middleware.ts
import { defineMiddleware } from "astro:middleware";

export const onRequest = defineMiddleware(async (context, next) => {
  if (context.request.method === "POST") {
    const token = context.request.headers.get("x-csrf-token");
    const expected = context.cookies.get("csrf")?.value;
    if (!token || token !== expected) {
      return new Response("Invalid CSRF token", { status: 403 });
    }
  }
  return next();
});

Common Pitfall

If this error appears intermittently, it likely points to a race condition or resource exhaustion issue rather than a simple misconfiguration. Check your connection pool settings and timeouts. Adding a comment in your configuration explaining why this setting exists will save your future self — and teammates — hours of confusion.

Verify the Fix

After applying the fix, restart your Astro application and verify the error no longer appears in the console or logs. Test both the happy path and edge cases to be thorough. If the error persists, double-check that your changes were saved and the application fully restarted.

Prevention

Consider integrating Bugsly into your Astro workflow to catch, track, and resolve errors like this automatically.