An exciting new area of action codes is the digital watermark, championed by companies like Digimarc. The advantage is that they are imperceptible to human senses, but can be quickly detected by mobile phones. The result is that marketers can have the advantages of action codes without impacting the design or using space required by a 2D barcode on the page.

Another advantage is that different watermarks can be placed in different parts of an ad or even a single photo. The result is the ability to create hot spots. For example, an advertisement with a photo of different fashion models can have a unique watermark for each fashion, each leading to different, relevant content online.

Marketers need to consider how to explain to a user that their advertisement contains a watermark. Unlike a 2D barcode, which are obvious on a page, a digital watermark does not have a visual cue unless one is explicitly created.

Digital watermarks from Digimarc are inexpensive at about $25 per code and are easily embedded into photos and other types of media.