[ui4jd73bdj]

Alert doesn't lock your browser. The developer can spend a lot of time and effort to make an even more intrusive and annoying custom alert.

Why should I as a user have to endure instagram and twitter blocking content with a delayed login prompt that cannot be canceled? Because they can. Browser APIs or not malicious developers will be malicious.

[oh_sigh]

Yes it does. You can't click on the URL bar and just navigate to a different site in chrome while an alert is displayed.

[ByteJockey]

You can in firefox (just tried from the console).

[slibhb]

I can.