Detect if user is online

The API

There is an API that let us check if the user is online:

navigator.onLine

and provide events triggered when going offline or online:

window.addEventListener('offline', () => console.log('now offline');
window.addEventListener('online', () => console.log('now online');

Possible usage

Some possible usages are:

• synchronizing data when going online with a PWA
• displaying an alert to the user if he looses connection when doing actions that requires him to be online

See also

• MDN doc
• An article by Chris Bongers