Editing Pop-up ad (section)

{{Short description|Form of online advertising}}
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{{Redirect|Pop-up window|pop-ups in general|dialog box|and|modal window}}
[[File:In-page pop-up window advertisement.jpg|thumb|Example of an in-page pop-up ad]]
'''Pop-up ads''' or '''pop-ups''' are forms of [[online advertising]] on the [[World Wide Web]]. A pop-up is a [[graphical user interface]] (GUI) display area, usually a small window, that suddenly appears ("pops up") in the foreground of the visual interface. The pop-up window containing an advertisement is usually generated by [[JavaScript]]<ref>{{cite web |title=How To Create Popups |url=https://www.w3schools.com/howto/howto_js_popup.asp |website=www.w3schools.com |access-date=26 October 2019}}</ref> that uses [[cross-site scripting]] (XSS), sometimes with a secondary payload that uses [[Adobe Flash]].<ref name=mozilla-noscript>{{cite web |url=https://addons.mozilla.org/firefox/addon/noscript |title=NoScript :: Add-ons for Firefox |work=[[Mozilla Add-ons]] |publisher=[[Mozilla]]}}</ref> They can also be generated by other [[Vulnerability (computing)|vulnerabilities/security holes]] in [[browser security]].

A variation on the pop-up window, the '''pop-under''' advertisement, opens a new browser window under the [[active window]]. Pop-unders do not interrupt the user immediately but appear when the user closes the covering window, making it more challenging to determine which website created them.