Electronic Frontier Foundation List of Printers Which Do or Do Not Display Tracking Dots
Introduction
This is a list in progress of color laser printer models that do or do not print yellow tracking dots on their output.
We are in the process of trying to interpret the information conveyed by these dots as part of our Machine Identification Code Technology Project.
Limitations of this information A "no" simply means that we couldn't see yellow dots; it does not prove that there is no forensic watermarking present. (For example, the HP Color LaserJET 8500 series does not include any yellow tracking dots that we can see, but it may still include some kind of forensic marking, since the majority of other Color LaserJET models do. Other forensic marking techniques have been invented, and we do not yet know how to determine whether these techniques are used by a particular printer.)
A "yes" simply means that we (or another source, as noted) saw yellow dots that appeared anomalous to us. Until we decipher the marking schemes or receive other confirmation, this does not constitute proof that any particular kind of information is represented by these dots. In a very few cases, for example, they might be the result of a dithering technique, rather than a forensic mark, or they could be the result of a poorly calibrated printer. In most cases, we are confident that the arrangement of dots is intentional and is intended to track users.
Sources of information We have employed three sources of information. We looked at printer output under a blue light and/or a computer microscope; we consulted press reports about printers (e.g. at Druckerchannel); we relied on printer manuals and other manufacturer statements. We welcome additional statements by manufacturers, resellers, or technicians.
Thanks to our friends at software firms and symphonies, public schools and physics labs, semiconductor fabs and ice cream parlors, in about a dozen countries around the world.
Table of printers
Click for Full Text! and chart of printers that allow THEM to track you down