Web/API/Window/alert

The Window.alert() method displays an alert dialog with the optional specified content and an OK button.

Syntax

window.alert(message);

Parameters

message Optional: A string you want to display in the alert dialog, or, alternatively, an object that is converted into a string and displayed.

Example

window.alert("Hello world!");
alert("Hello world!");

Both produce:

[[File:../../../../../../media.prod.mdn.mozit.cloud/attachments/2012/07/09/130/544165b82dc2d1e62e3fc8585b1ede4d/AlertHelloWorld.png|Image:AlertHelloWorld.png]]

Notes

The alert dialog should be used for messages which do not require any response on the part of the user, other than the acknowledgement of the message.

The following text is shared between this article, DOM:window.prompt and DOM:window.confirm Dialog boxes are modal windows - they prevent the user from accessing the rest of the program's interface until the dialog box is closed. For this reason, you should not overuse any function that creates a dialog box (or modal window).

Specification

Specification	Status	Comment
HTML Living StandardThe definition of 'alert()' in that specification.	Living Standard

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`alert`	Chrome Full support 1 Notes' Full support 1 Notes' Notes' Starting with Chrome 46, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.	Edge Full support 12	Firefox Full support 1	IE Full support 4	Opera Full support 3 Notes' Full support 3 Notes' Notes' Starting with Opera 33, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.	Safari Full support 1	WebView Android Full support 1 Notes' Full support 1 Notes' Notes' Starting with WebView 46, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.	Chrome Android Full support 18 Notes' Full support 18 Notes' Notes' Starting with Chrome 46, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.	Firefox Android Full support 4	Opera Android Full support 10.1 Notes' Full support 10.1 Notes' Notes' Starting with Opera 33, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.	Safari iOS Full support 1	Samsung Internet Android Full support 1.0 Notes' Full support 1.0 Notes' Notes' Starting with Samsung Internet 5.0, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.

Legend

Full support: Full support
See implementation notes.': See implementation notes.