Interstitials or interstitial ads are web banners that interrupt a user’s visit on a website and use this attentiveness for advertising purposes. Interstitials can be realized in different ways and also come in handy for mobile advertising. A common form of interstitials is the so-called pop-up. The word interstitial is derived from interstice, which means an intervening space. This form of advertising first creates an intervening space between the user and the website being viewed. In most cases, one also speaks of “commercial breaks”. Since January 2017, Google potentially penalizes websites for excessive use of interstitials on mobile websites. 
Advertising in general and banner advertising on the Internet, in particular, has one major drawback: the person becomes accustomed and eventually ends up not paying attention to the advertisement. What happens in online advertising is, for instance, the so-called banner blindness. This is when users no longer view banners as advertisements and do not pay attention any more to the content. In order to obtain the greatest possible attention for advertisements, markets are always looking for new solutions. The interstitial is one of them.
The display of interstitials is triggered by different actions. These include:
The interstitial is either automatically hidden again after a certain time interval or the user has to close it manually.
Interstitials can appear in different forms and are flexible in terms of size and configuration. Normally, interstitials are loaded directly in the same browser window. These are called inline interstitials. Other types include:
Interstitials are often associated with a high efficiency, since they mostly appear unexpectedly for users. Thus, interstitials are an effective means of advertising. They are ideal for drawing attention towards special offers within the framework of a campaign and promoting branding. In addition, due to their special position, interstitials do not have to compete with other banners. Through the multimedia character and the ability to be use the entire browser window, web designers have an almost unlimited design freedom. Videos, photos, or songs, i.e. rich media, can be played using interstitials. Furthermore, the user has no way of escaping the advertising message, unless he/she clicks on the back button or closes the browser window.
However, this results in one disadvantage. If their use is not contemplated correctly, they can lead to uncertainty on the part of the user in extreme cases (“What did I just click on?”, “I only wanted to look up a new cake recipe, why is the screen showing an SUV?”) or even preventing the user from visiting the page again. Therefore, interstitials and superstitials should be designed carefully and tailored to the target audience.
Another disadvantage of interstitials is that they can cause a loss in rankings when used on mobile websites. In August, Google introduced a new algorithm that imposes a penalty on mobile websites when they are overlaid with a certain form of interstitial. Google sees these interruptions as a sign of a worse User Experience.