---
title: "Why am I getting CORS errors on preflight requests and how to fix them?"  
description: "Why am I getting CORS errors on preflight requests and how to fix them?"  
author: "Manish Sharma"  
published: 2026-09-19  
canonical: https://answers.mindstick.com/qa/117238/why-am-i-getting-cors-errors-on-preflight-requests-and-how-to-fix-them  
category: "Web Development"  
tags: ["javascript", "cors", "express", "react", "node-js"]  
reading_time: 1 minute  

---

# Why am I getting CORS errors on preflight requests and how to fix them?

I am building a React frontend that connects to a Node.js Express backend hosted on a separate domain. Simple GET requests work fine, but POST and PUT requests fail with a [CORS error](https://www.mindstick.com/forum/159708/how-to-solve-cors-error-in-net-core-api) during the preflight phase. How should OPTIONS requests be handled correctly on the server?

## Express CORS Configuration

Preflight requests use the HTTP **OPTIONS** method. Here is how to configure Express to return proper CORS headers.

```js
const express = require('express');
const app = express();

// Handle CORS preflight explicitly
app.use((req, res, next) => {
    // Allow requests from frontend domain
    res.header('Access-Control-Allow-Origin', 'https://app.example.com');
    // Specify allowed headers
    res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept, Authorization');
    // Specify allowed HTTP methods
    res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');

    // Intercept preflight OPTIONS request
    if (req.method === 'OPTIONS') {
        return res.sendStatus(200);
    }
    next();
});
```

### Debugging Checklist

- Verify that response headers match the exact origin instead of wildcards when using credentials
- Check if reverse proxies (like Nginx) strip CORS headers
- Ensure status code 200 or 204 is returned for OPTIONS requests


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Original Source: https://answers.mindstick.com/qa/117238/why-am-i-getting-cors-errors-on-preflight-requests-and-how-to-fix-them

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