Popup
A new browser window that appears unrequested (by you) on your screen. A gratuitous, easily-programmed visual effect exploited by many web sites often to the consternation of the hapless user.

Exit popup
A window that springs to life when you leave a site or close a browser window. We have never met one that was useful. Modern browsers refuse to open windows during page close, which is why our old exit-popup tests are retired.

Popup blocker (also called popup stopper, ad blocker, or ad killer)
A program that stops unsolicited windows from appearing on your screen; these windows usually contain advertisements. Different names, same job. Browsers build this in now, and our popup test scores how well yours does it.

Popup test (also called popup check)
A page that checks your blocker's ability to stop the windows you did not ask for and allow the ones you did. Ours scores from 1 to 100.

Floating popup
Not a real window at all, just a piece of the page dressed up to look like one. A popup blocker cannot stop it because there is no window to block. Some test sites use these to fail your blocker on purpose; there is a demo on our home page.

Pop-under
A popup that opens behind your window instead of in front of it, so you only find it after you close your browser. Sneakier than the classic popup, and part of our test.

Chained popup
A popup that opens another popup, which opens another. This was the engine behind the old popup storms that buried desktops in ads. Our advanced pop-up test checks for it.

Mouse-over popup
A popup fired by resting your pointer on something. Hovering is not clicking, so a good blocker treats it as unsolicited.

Net Send Spam (Messenger spam)
An old Windows Messenger vulnerability, also called net send spam or winpopup. These ads took the form of a gray box bearing spam with an OK button. The versions of Windows that allowed it are long gone.

Adware
While not necessarily malware, adware goes beyond the reasonable advertising you might expect from freeware or shareware. It usually arrives as a separate program installed alongside the one you wanted, and it keeps serving ads even when the original program is not running.

Spyware
A general term for a program that quietly monitors your actions. Sometimes it is sinister, like a remote control program used by a hacker. Software companies have also been known to use spyware to gather data about customers. The practice is generally frowned upon.

Malware
A generic term for any form of malicious software: viruses, trojan horses, malicious active content, and the rest.

Spam
Unsolicited junk email sent in bulk to promote products or services. The term also covers inappropriate promotional postings to forums and comment sections. Our spam filter page covers what still works against it.

AntiSpam
Software or a service that helps prevent unsolicited mail and complicates a spammer's method of collecting email addresses.