Fixing Failed to Fetch errors in JavaScript

Stephen Cefali

—January 22, 2024

Fixing “TypeError: Failed to Fetch” Errors in JavaScriptFixing “TypeError: Failed to Fetch” Errors in JavaScript

IntroductionIntroduction

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” ErrorsCommon Causes of “Failed to Fetch” Errors

Incorrect or Incomplete URLIncorrect 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) IssuesCORS (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.
• Server configuration should include appropriate Access-Control-Allow-* headers.

Incorrect Fetch ConfigurationIncorrect 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 ExtensionsBrowser Extensions

• Sometimes, browser extensions can cause these errors. They might interfere with the API calls or modify the responses.

Steps to DebugSteps to Debug

Check the URLCheck 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 ConsoleExamine 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 HeadersVerify 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 ConfigurationsTest with Different Configurations

• Experiment with different fetch configurations to isolate the issue.
• Try changing methods, headers, and URL formats.

Consider Proxy UsageConsider 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.