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Network/connectivity issue

Fixing Failed to Fetch Errors

TypeError: Failed to fetch has multiple root causes. You need to isolate URL, CORS, HTTPS, and DNS step by step.

TL;DR

1) Verify API URL and env vars 2) Confirm request appears in Network tab 3) Check CORS / mixed content / certificate issues

심각

TypeError: Failed to fetch

원인

Browser failed to complete the request due to network/CORS/SSL/DNS/backend issues.

해결책
  1. Check if request is sent in browser Network tab
  2. Validate API base URL and environment variable values
  3. Verify request reaches backend logs
  4. Inspect CORS and HTTPS mixed content rules

Quick checks

fetch.ts
const apiUrl = import.meta.env.VITE_API_URL;

if (!apiUrl) {
  throw new Error('VITE_API_URL is missing');
}

const response = await fetch(apiUrl + '/health', {
  method: 'GET',
  credentials: 'include',
});
wrong vs correct
# Wrong
https://app.example.com -> http://api.example.com

# Correct
https://app.example.com -> https://api.example.com

Practical tip

This error message alone is too generic. Always inspect both browser Network panel and backend logs together.

Prerequisites

  • You can inspect failed request URL/method/headers in DevTools.
  • You can read backend logs for the same request.
  • You can classify whether issue is DNS/SSL/CORS/network.

Validation

  1. Request appears in Network tab with expected status code.
  2. Backend receives the request and returns expected response.
  3. Frontend renders data without fetch exceptions.

Troubleshooting

  • Verify base URL config for each environment.
  • Check mixed content (HTTPS page calling HTTP API).
  • If preflight fails, validate OPTIONS handling first.

References

Related Articles

CORS Error

Cross-origin request failures

SSL Certificate Error

HTTPS/TLS issues

Last updated: February 22, 2026 · Version: v0.0.1

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