What does your printer do for the government?

Yellow dots (texture by Patrick Hoesly - CC-BY)

Does your printer simply receive data from your computer and spit out printed pages? Or does it do more than that?

At least nine printer manufacturers make printers that do more than just print your page:

  • Canon
  • Brother
  • Casio
  • HP
  • Konica Minolta
  • Mita
  • Ricoh
  • Sharp
  • Xerox

According to a 2012 request under the US Freedom of Information Act, those printer manufacturers “have fulfilled or agreed to fulfill documentation identification requests submitted by the Secret Service … using machine identification code technology”.

The printer overlays the image you want to print with a pattern of tiny yellow dots. These dots encode the serial number of the printer, the date and time of the print, and possibly other information. This forensic information can be used to confirm that a printout originated from a specific printer.

A similar idea was employed by Romania and other communist countries last century. Every typewriter had to be registered. The specific blemishes characteristic to the output of each typewriter would be recorded, so that any typewritten page could be traced back to the typewriter on which it was produced.

The yellow pattern that is added to your printed page causes several problems:

  • it degrades the quality of the image,
  • it increases the cost of ink or toner, and
  • it causes annoyance when the printer will not print a black-and-white page because the yellow ink has run out.

It’s not just printers that add dots to your output. Many color photocopiers also add yellow dots to the pages they produce. These dots are not usually visible, but you can see them if you know what to look for. They are easier to spot under blue light, or with the aid of a magnifying glass.

In 2005, the Electronic Fronteir Foundation published a list of printers on which the dots had been found (or not found). Of the printers examined, no dots were found on any printer made by OkiData or Samsung.

Many printers and photocopiers also refuse to print images that resemble currency. They detect currency by a variety of means, some of which are publicly known. One method which is known is the EURion constellation, a repeated pattern of five small circles printed in a light color and incorporated into the design of the note.

Some image editing software will detect an attempt to edit a scanned image of a banknote, and reject the action. There are some legitimate reasons why you might want to edit an image that has been derived from a banknote. This can be done using open source image editing software such as The Gimp, which does not have this “added feature”. You can look up the legal restrictions on the reproduction of banknote images at

You can use the Eurionize app to add the EURion “constellation” to your own PDF files. This will prevent your document from being copied on most color copiers. As the Eurionize site points out, there are numerous ways to defeat this system, so it only provides “a small increase in security of documents like coupons and entertainment admission tickets”.


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