Every page in your office colour laser printer contains yellow dots that are too small for the average person to see. The dots form patterns that allow the printer’s make and model to be identified. Printer companies added the dots at the request of the US government in order to trace documents back to the printer. The Electronic Freedom Foundation, a civil rights and technology organisation, has investigated the use and nature of these yellow dots.
Information Printed
Color laser printers’ yellow identifying dots contain information identifying the printer’s make, model, and serial number. The dots identify the current date and time if the printer has them. The exact information contained in the dot patterns is known only to printer manufacturers and the government, though outside investigators have partially deciphered its meaning.
Affect on Documents
The yellow colour contrasts poorly with white paper, making the dots difficult to see with the naked eye. The dots are generated by the laser printing mechanism. In most cases, the dots have no effect on the quality of photos, graphics, or other documents printed on laser printers. Because the dots are so small, they have no effect on toner consumption.
Purpose
As the resolution of colour copiers and laser printers has improved, the technology has simplified money counterfeiting and other types of forgery, which is why the FBI and the US Secret Service have asked equipment manufacturers to develop a method that allows law enforcement to detect counterfeit money produced on these machines and then trace the currency back to its source.
Types of Printers Affected
Yellow dot technology appears to be restricted to colour laser printers and copiers. Because monochrome laser, LED, and inkjet printers lack the yellow toner required to print the dots, these markings are not produced. Furthermore, because Xerox developed the yellow dot technology in the 1990s, this only affects printers manufactured since then. Yellow dot marks have been found on documents from a variety of printer manufacturers, including Xerox, Hewlett-Packard, Toshiba, and Canon. According to the Electronic Freedom Foundation, experts are unaware of any other secret identifying marks in printed materials at the time of publication.
Making Dots Visible
By shining a bright blue light on a printed document, you can increase the contrast of the yellow dots. Light from a blue LED “keychain” source, for example, turns the yellow dots black, making them more visible. A page with little content is an excellent candidate because the black dots stand out more against a blank background.
