Returns the online status of the browser. The property returns a boolean value, with true meaning online and false meaning offline. The property sends updates whenever the browser's ability to connect to the network changes. The update occurs when the user follows links or when a script requests a remote page. For example, the property should return false when users click links soon after they lose internet connection.

Browsers implement this property differently.

In Chrome and Safari, if the browser is not able to connect to a local area network (LAN) or a router, it is offline; all other conditions return true. So while you can assume that the browser is offline when it returns a false value, you cannot assume that a true value necessarily means that the browser can access the internet. You could be getting false positives, such as in cases where the computer is running a virtualization software that has virtual ethernet adapters that are always "connected." Therefore, if you really want to determine the online status of the browser, you should develop additional means for checking. To learn more, see the HTML5 Rocks article, Working Off the Grid.

In Firefox and Internet Explorer, switching the browser to offline mode sends a false value. Until Firefox 41, all other conditions return a true value; since Firefox 41, on OS X and Windows, the value will follow the actual network connectivity.

You can see changes in the network state by listening for the events on window.ononline and window.onoffline.


online = window.navigator.onLine;


online is a boolean true or false.


View a live example.

To check if you are online, query window.navigator.onLine, as in the following example:

if (navigator.onLine) {
} else {

If the browser doesn't support navigator.onLine the above example will always come out as false/undefined.

To see changes in the network state, use addEventListener to listen for the for the events on window.ononline and window.onoffline, as in the following example:

window.addEventListener("offline", function(e) { console.log("offline"); });

window.addEventListener("online", function(e) { console.log("online"); });


Specification Status Comment
WHATWG HTML Living Standard
The definition of 'navigator.onLine' in that specification.
Living Standard Initial definition

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support (Yes)[1] 3.5 (1.9.1)[2]
4.0 (2.0)[4]
8[3] No support[2] 5.0.4
on WorkerNavigator Yes 29 (29) ? ? ?
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile BlackBerry
Basic support 2.2[5] 1.0 (1.9.1)[2] ? ? ?


on WorkerNavigator ? 29.0 (29) ? ? ? ?

[1] Earlier versions of Chrome incorrectly return true when a tab is first opened, but it starts reporting the correct connectivity status after the first network event. Windows: 11, Mac: 14, Chrome OS: 13, Linux: Always returns true. For history, see

[2] Since Firefox 4, and Opera 11.10, the browser returns true when "Work Offline" mode is disabled and false when it is enabled, regardless of actual connectivity.

[3] in Internet Explorer 8 "online" and "offline" events are raised on the document.body; under IE 9 they are raised on both document.body and window.

[4] Since Firefox 41, on OS X and Windows, the returned values follow the actual network connectivity, unless "Work offline" mode is selected (where it will always return false).

[5] Faulty in a WebView component, see Issue bug 16760.


See Online/Offline Events‎ for a more detailed description of this property as well as new offline-related features introduced in Firefox 3.

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API DOM Reference NavigatorOnLine Online Property Reference