I am referring to the yellow dots which are printed automatically by laser printers. They encode information such as the time the document is printed as well as the serial number. There appears to be quite little information on this subject available on the internet.

I would like to know if anyone has heard of any known cases out there where law enforcement managed to identify the specific printer which produced the document? Is this something viable that could be used to detect corporate espionage or is this a failed attempt that has long been abandoned?

Links for more information:



1 Answer 1


The EFF has a page describing how the information is encoded in those yellow dots:

The Python program to decode can be found at: https://github.com/zackdouglas/docucolor.cgi

They also published a list of printers which do not display those dots:

I'm not aware of cases where law enforcement declared they used them but I suppose it's common knowledge in any forensic lab since the printer manufacturers were most likely pressured to have that function implemented as it does increase the cost of development and production (even marginally).


Ok, I just found out the EFF has a page with all their FOIA requests regarding the use of printer dots and other watermarking by law enforcement agencies (~700 pages total in 6 PDF files), they were released in 2008:


Edit: EFF suggests that any color printer from a major manufacturer add some kind of tracking code.

  • The information on those pages including the list of printers is more than 10 years old. That is why I want to know if this is still a viable technique today and do today's printers still have watermarks. Dec 18, 2014 at 14:54
  • 1
    The EFF link fails. I couldn't find a link to it.
    – kelalaka
    Oct 2, 2018 at 8:47

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