# Fix TypeError Failed to Fetch in JavaScript

> Debug and fix TypeError Failed to Fetch errors in JavaScript caused by incorrect URLs, CORS misconfigurations, bad request headers, or browser extensions

**URL:** https://sentry.io/answers/failed-to-fetch-javascript/

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## Introduction

The "TypeError: Failed to fetch" error can be a common and frustrating issue when working with web applications. This error is typically triggered by issues with the Fetch API, and there are several reasons why it might occur.

## Common Causes of "Failed to Fetch" Errors

### Incorrect or Incomplete URL
- The URL passed to the `fetch()` method might be incorrect or incomplete.
- Ensure the URL includes the correct protocol (`https://` or `http://`), and the path is accurate.

### CORS (Cross-Origin Resource Sharing) Issues
- The server might not send back the correct CORS headers. If you're not sure what CORS is, check out the [MDN Docs]( https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS).
- Server configuration should include appropriate `Access-Control-Allow-*` headers.

### Incorrect Fetch Configuration
- Errors in the HTTP method or headers passed to the `fetch()` method.
- Verify the correct configuration, including URL, HTTP method, and headers.

### Browser Extensions
- Sometimes, browser extensions can cause these errors. They might interfere with the API calls or modify the responses.

## Steps to Debug

### Check the URL
- Ensure the URL used in the `fetch()` method is correct and complete.
- Check for protocol, path accuracy, and HTTP method appropriateness.

### Examine Browser Console
- The browser console can provide more information about the failed API calls.
- Look for errors related to CORS or other network issues.

### Verify CORS Headers
- Check if the server is sending the correct CORS headers.
- Use the browser's Network tab to inspect the headers of the failed requests.

### Test with Different Configurations
- Experiment with different fetch configurations to isolate the issue.
- Try changing methods, headers, and URL formats.

### Consider Proxy Usage
- If modifying server headers isn't feasible, use a proxy to bypass CORS issues.
- Implement proxies using tools like `express` or `cors-anywhere` in Node.js.

## Monitoring Network Errors in Production

While debugging "Failed to Fetch" errors locally helps identify configuration issues, [JavaScript error monitoring](https://sentry.io/for/javascript/) in production captures the full context of network failures. Production environments surface issues that don't appear in development—intermittent network problems, region-specific API outages, or CORS configurations that only fail for certain users. Error monitoring tools automatically capture these fetch failures with request details, user context, and network conditions, making it easier to diagnose whether issues stem from your code, your API, or external factors.

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*Source: [sentry.io/answers/failed-to-fetch-javascript/](https://sentry.io/answers/failed-to-fetch-javascript/)*