Fix JavaScript ReferenceError: fetch is not defined (2025 Guide)

Fix ReferenceError: fetch is not defined in JavaScript - 2025 Guide

Posted on: March 24, 2025

Getting a "ReferenceError: fetch is not defined" in JavaScript? It’s because fetch isn’t available in Node.js by default. Let’s fix it fast in this 2025 guide!

What Causes "ReferenceError: fetch is not defined"?

This error occurs when you use the fetch API in Node.js, where it’s not natively supported (prior to Node.js 18). Common causes:

• Node.js Environment: fetch is a browser API, not part of older Node.js core.
• Missing Library: No external fetch implementation installed.
• Environment Confusion: Mixing browser and Node.js code.

Test this locally (create main.js and run node main.js):

// main.js
fetch('https://api.example.com')
  .then(response => response.json())
  .then(data => console.log(data));
// Run: node main.js

This will throw "ReferenceError: fetch is not defined."

Check a browser-compatible fetch demo (open console with F12):

How to Fix It: 3 Solutions

Let’s resolve this error with practical steps:

(Diagram: Developer uses fetch, gets error, adds node-fetch, runs successfully.)

Solution 1: Use node-fetch in Node.js

Install and use the node-fetch package:

// Run: npm install node-fetch
const fetch = require('node-fetch');

fetch('https://api.example.com')
  .then(response => response.json())
  .then(data => console.log(data))
  .catch(error => console.error(error));

Install with npm install node-fetch and require it.

Solution 2: Use Undici (Node.js Built-in)

Use Node.js 18+ built-in undici fetch alternative:

const { fetch } = require('undici');

fetch('https://api.example.com')
  .then(response => response.json())
  .then(data => console.log(data))
  .catch(error => console.error(error));

Available in Node.js 18+ without additional installation.

Solution 3: Switch to Browser Environment

If possible, run the code in a browser:

fetch is natively supported in browsers.

Quick Checklist

• Node.js environment? (Install node-fetch or use undici)
• Browser possible? (Use native fetch)
• Correct setup? (Verify package installation)

Conclusion

A "ReferenceError: fetch is not defined" is a common issue in Node.js, but with these 2025 solutions, you’ll handle API calls smoothly. Got another JavaScript error to solve? Let us know in the comments!