Check if the internet connection is up

Works in Node.js and the browser (with a bundler).

In the browser, there is already navigator.onLine, but it's useless as it only tells you if there's a local connection, and not whether the internet is accessible.

npm install is-online

• Node.js 20+
• Works in modern browsers when bundled (requires fetch API support)

import isOnline from 'is-online';

console.log(await isOnline());
//=> true

import isOnline from 'is-online';

console.log(await isOnline({timeout: 10_000}));
//=> true

import isOnline from 'is-online';

const controller = new AbortController();

setTimeout(() => {
	controller.abort();
}, 500);

const result = await isOnline({
	timeout: 3000,
	signal: controller.signal
});

console.log(result);
//=> false

import isOnline from 'is-online';

const result = await isOnline({
	fallbackUrls: [
		'https://www.google.com',
		'https://www.github.com',
		'http://example.com'
	]
});

console.log(result);
//=> true

Returns a Promise<boolean> that resolves to true if the internet connection is up, false otherwise.

Type: object

Type: number
Default: 5000

Milliseconds to wait for a server to respond.

Type: AbortSignal

An AbortSignal to abort the operation.

When the signal is aborted, the promise will resolve to false.

Type: number
Values: 4 | 6
Default: 4

The Internet Protocol version to use.

This is an advanced option that is usually not necessary to be set, but it can prove useful to specifically assert IPv6 connectivity.

Type: string[]

Fallback URLs to check for connectivity.

Only HTTP and HTTPS URLs are supported. In Node.js, these URLs are checked only if all default connectivity checks fail. In the browser, these URLs are checked in parallel with the default checks for better resilience against ad blockers.

The following checks are run in parallel:

Node.js:

• Retrieve icanhazip.com (or ipify.org as fallback) via HTTPS.
• Query myip.opendns.com and o-o.myaddr.l.google.com DNS entries.
• Retrieve Apple's Captive Portal test page (this is what iOS does).
• Check Cloudflare's website via HTTPS.

Browser:

• Retrieve icanhazip.com (or ipify.org as fallback) via HTTPS.

When any check succeeds, the returned Promise is resolved to true.

If all the above checks fail and you have provided fallbackUrls, those will be checked as a fallback. The URLs are checked by making HTTP/HTTPS requests (HEAD requests when possible, with GET as fallback).

The package publishes diagnostic information when connectivity checks fail using Node.js Diagnostics Channel. This is useful for debugging network issues and is only available in Node.js environments.

import {subscribe} from 'node:diagnostics_channel';
import isOnline from 'is-online';

// Subscribe to failure events
subscribe('is-online:connectivity-check', message => {
	console.log('Failed URL:', message.url);
	console.log('Error:', message.error);
});

await isOnline();

Each failure event includes:

• timestamp - When the failure occurred
• url - The specific URL that failed
• error - Error details (name, message, code)

To make it work through proxies, you need to set up global-agent.

• Sindre Sorhus
• silverwind

• is-online-cli - CLI for this module
• is-reachable - Check if servers are reachable