Most color printers from the most trusted brands use this tracking dot system, placing an array of small dots on every document you print, even if you tell them to use only black and white ink. These points can be read by someone familiar with a manufacturer’s coding system to determine the precise make and model of your printer, the date and time you used it, and, in some cases, whether you were printing a document alone or copying another. The practice has its roots in both coded messages sent during World War II and counterfeiting prevention measures used on bank notes.
Dots reveal the original printer and when something was printed
If you look closely at any document printed from your color printer, either with a microscope or under special lighting, you will see a multitude of dots arranged in a grid pattern. These dots are printed in an extremely light shade of yellow that you can’t see with the naked eye, but they are definitely there. Your printer adds these dots to each print job, their arrangement in the grid serving as identifying markers. These markers, also called machine identification codes, serve as a digital fingerprint for your printer. By analyzing the markers and knowing a manufacturer’s encoding practices, you can get a complete read of which printer the document came from, as well as the exact day and time it was printed.
There is no publicly stated reason why printer manufacturers are adding this feature, but the consensus is that it is to help forensic investigators detect counterfeits, in the same vein as the microscopic dots placed on bank notes. A random person could print a document and say they got it from a specific source or individual a long time ago, for example, but looking at the tracking points would reveal that it came from their own printer last week, thus disputing their claim. In fact, the first color printers produced by Xerox in the 1980s specifically used this system, so they could not be used to forge bank notes.
