I'm wondering if can I change the window.beforeunload message. All examples on the internet are similar to this:

$(window).bind('beforeunload', function() {
    return 'You have unsaved changes. If you leave the page these changes will be lost.';
});

That's cool, and in Google Chrome my message will be displayed, but in Firefox the default message is displayed. How can i trick Firefox to display my message and not the default message?

I'm wondering if can I change the window.beforeunload message. All examples on the internet are similar to this:

$(window).bind('beforeunload', function() {
    return 'You have unsaved changes. If you leave the page these changes will be lost.';
});

That's cool, and in Google Chrome my message will be displayed, but in Firefox the default message is displayed. How can i trick Firefox to display my message and not the default message?

• javascript
• jquery

Share Improve this question Follow edited Feb 8, 2013 at 15:52 gen_Eric 227k4242 gold badges303303 silver badges342342 bronze badges asked Feb 8, 2013 at 13:13 SoraSora 2,5511919 gold badges7777 silver badges151151 bronze badges 4

• 1 Firefox (version 4+) doesn't support custom messages on onbeforeunload anymore. bugzilla.mozilla/show_bug.cgi?id=588292 – gen_Eric Commented Feb 8, 2013 at 15:45
• 1 @RocketHazmat you might want to add that as an answer. For points and whatnot. Update: I see you have 50k points, you probably already know how this works. Disregard. – Felix Commented Feb 8, 2013 at 15:57
• @Felix: Sometimes when answers are just "you can't" or "that's how it works", I don't feel like typing an entire answer :-P Alas, I added one anyway :-) – gen_Eric Commented Feb 8, 2013 at 16:15
• Chrome no longer displays the custom message returned from beforeunload. chromestatus./feature/5349061406228480 – jimp Commented Jun 20, 2017 at 23:01

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1 Answer 1

Sorted by: Reset to default 6

onbeforeunload is a weird event. Browsers have been debating what to do with it for a while.

• IE and Chrome will display your message in the dialog along with their own message.
• Firefox used to display your message, but in version 4+, they stopped supporting custom messages. See this: https://bugzilla.mozilla/show_bug.cgi?id=588292
• Opera doesn't even support the onbeforeunload method!

This method is under debate because it can be used for evil, and also because it can confuse/annoy users. Scammy, virus-laden sites can use messages like:

"Leaving the page will mean your puter may still be infected, please stay and install our virus scanner"

Nowadays, websites can use AJAX / localStorage to save changes, so this event isn't really needed.