Network & HTTP · Developer Error Resolution Lab

Fix JavaScript 'TypeError: Failed to fetch' in Browser & Node.js

Diagnose network drops, CORS blocks, HTTPS certificate invalidity, and ad-blocker request cancellations.

Fix Guide:

Triggered Error Message:

TypeError: Failed to fetch (at window.fetch)

Customize Solution for Your Environment

Target API URL

async function safeFetch() {
  const controller = new AbortController();
  const timeoutId = setTimeout(() => controller.abort(), 10000); // 10s timeout

  try {
    const res = await fetch("https://api.example.com/v1", {
      signal: controller.signal,
      headers: { "Content-Type": "application/json" }
    });

    if (!res.ok) throw new Error(`Server returned ${res.status}`);
    return await res.json();
  } catch (err: any) {
    if (err.name === "AbortError") {
      console.error("Request timed out after 10s");
    } else {
      console.error("Network or CORS failure:", err.message);
    }
    throw err;
  } finally {
    clearTimeout(timeoutId);
  }
}

Root Cause & Mechanism Analysis

Why does this error occur?

Generic browser error thrown when a network request fails before receiving an HTTP response: triggered by CORS preflight rejections, DNS resolution failures, offline network, or mixed content (HTTP on HTTPS).