Is Customizing the BeforeUnload Popup Message Still Possible?

Displaying Custom Message in BeforeUnload Popup: Still Viable?

When handling window closing events with window.onbeforeunload or jQuery's $(window).on("beforeunload"), one might wonder if displaying a tailored message in the ensuing confirmation popup is feasible.

Bypassing Modern Browsers' Restriction

TL;DR: In present-day browsers, customizing the beforeunload message is prohibited. Our focus, therefore, reverts to legacy browsers.

Leveraging jQuery and JavaScript

To prompt the user with a confirmation message, employ the following code:

// jQuery
$(window).bind("beforeunload", function(event) {
    return "Attention required: Unsaved changes present";
});

// JavaScript
window.onbeforeunload = function() {
    return "Exiting this page may abandon form inputs";
};

Critical Exception: Inhibiting Confirm/Alert Functions

Refrain from nesting confirm or alert within the beforeunload event handler.

Browser-Specific Considerations

The effectiveness of this method varies across browsers:

• Chrome, Opera, and Safari no longer support custom messages.
• Firefox requires user interaction with the page to trigger the prompt.
• Each browser may append additional text to your message.

Historical Context

Custom messages in beforeunload were once feasible using methods such as confirm, alert, or event.returnValue, but subsequent browser updates have rendered these approaches ineffective.

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