Widely available Supported across all major browsers. Safe to use in production.

Alerts

window.alert() instructs the browser to display a dialog with an optional message, and to wait until the user dismisses the dialog.

Under some conditions — for example, when the user switches tabs — the browser may not actually display a dialog, or may not wait for the user to dismiss the dialog.

Display and Navigation

Browser support

Feature Desktop Mobile
Chrome
Edge
Firefox
Safari
Chrome Android
Safari iOS
alert
1
12
1
1
18
1
confirm

window.confirm() instructs the browser to display a dialog with an optional message, and to wait until the user either confirms or cancels the dialog.
1
12
1
1
18
1
prompt

window.prompt() instructs the browser to display a dialog with an optional message prompting the user to input some text, and to wait until the user either submits the text or cancels the dialog.
1
12
1
1
18
1
1+Supported (version) Not supported ※Has note Sub-feature descriptions sourced from MDN Web Docs (CC BY-SA 2.5)
Notes 1 item(s)
Implementation note
  • Starting with Chrome 46, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.
Notes 1 item(s)
Implementation note
  • Starting with Chrome Android 46, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.
Notes 1 item(s)
Implementation note
  • Starting with Chrome 46, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.
Notes 1 item(s)
Implementation note
  • Starting with Chrome Android 46, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.
Notes 1 item(s)
Implementation note
  • Starting with Chrome 46, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.
Notes 1 item(s)
Implementation note
  • Firefox strips newline characters from the prompt response; see bug 1716229.
Notes 1 item(s)
Implementation note
  • Starting with Chrome Android 46, this method is blocked inside an `<iframe>` unless its sandbox attribute has the value `allow-modals`.

Syntax

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

Use cases

  • Using Alerts

    window.

Cautions

  • May not be supported in older browsers.

Implementation notes

  • Some APIs require a secure context (HTTPS) or user activation. Check the requirements before use.

Related links