HTML DOM Window alert() Method

Last Updated : 11 Jul, 2025

The alert() method in HTML and JavaScript is used to display an alert box with a specified message. The alert box includes an OK button and is typically used to ensure that the user receives critical information or confirmation before proceeding.

Note: Alert boxes grab your attention and make you read a message and Using too many alerts stops you from doing other things on the webpage until you close them.

Syntax

alert(message);

Parameter:

Message: It is the message that is needed to show in the alert box and it's optional.

Example: Display an alert box by double-clicking a button.

In this example the alert() is used to display a message box when the button is double-clicked. The message informs users about GeeksforGeeks. It's a simple way to show notifications or information.

html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" 
          content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <h1 style="color: green;">
        GeeksforGeeks
    </h1>
    <p>
        For displaying the alert message, double
        click the "Show Alert Message" button:
    </p>

    <button ondblclick="myalert()">
        Show Alert Message
    </button>

    <script>
        function myalert() {
            alert("Welcome to GeeksforGeeks.\n " +
                "It is the best portal for computer" +
                "science enthusiasts!");
        }
    </script>
</body>

</html>

Output:

Example: Alert the hostname of the current URL

In this example we displays the hostname of the current URL when the "Show Hostname" button is clicked. The showHostname() function retrieves the hostname using window.location.hostname and shows it in an alert box.

HTML

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" 
          content="width=device-width, initial-scale=1.0">
    <title>Alert Hostname Example</title>
</head>

<body style="text-align: center;">
    <h1 style="color: green;">
        Geeks
    </h1>
    <p>
        To see the hostname of the current URL,
        click the "Show Hostname" button:
    </p>

    <button onclick="showHostname()">
        Show Hostname
    </button>

    <script>
        function showHostname() {
            let currentURL = window.location.hostname;
            alert("The hostname of the current URL is: " + currentURL);
        }
    </script>
</body>

</html>

Output:

jiu

Supported Browsers:

HTML DOM Window alert() Method

S

Shubrodeep Banerjee

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