Semantics: overlays versus pop-ups
Here’s a typical overlay:
A pop-up is a new browser window that’s smaller than the one behind it. These were used to serve ads for many years, so many people have installed pop-up blockers to prevent them from opening. Because of this, it’s recommended that we never use pop-ups on our websites. Even if you haven’t installed a pop-up blocker in your own browser, you may notice that you’re not getting pop-up ads anymore. This is because the industry has for the most part abandoned them due to the above reasons.
Here’s a typical pop-up:
A lot of people use the terms “overlay” and “pop-up” interchangeably, and this is a little bit dangerous. Nowadays we’re almost always talking about overlays — we should not be using actual pop-ups for anything. If a client knows their stuff and we tell them we’re using a “pop-up” when we mean an overlay, they might think we don’t know what we’re talking about. If we want to look like we’re digitally savvy, it’s important we use the right terms.
I’ve also occasionally heard people refer to an overlay as a lightbox. When overlays were relatively new, some photography websites called them lightboxes, since they were used to display a photo at a larger size over a transparent black mask. Although lightbox is not an incorrect term, it’s really only relevant to photography, and it’s not relevant to the overlays we’re creating on our websites, which usually contain more than just a photo.