Yellow Dots of Mystery: Is Your Printer Spying on You?


Imagine that every time you print a document, it automatically includes a secret code that could be used to identify the printer -- and, potentially, the person who used it. Sounds like something from a spy movie, right?

Unfortunately, the scenario isn't fictional. Most color laser printers and color copiers are designed to print invisible tracking codes across every single printed page of their output. These codes reveal which machine produced a document and, in some cases, when the document was printed or copied.

In this instructable, we'll describe three different ways to see the tracking dots your printer produces: with a blue light, with a microscope, or with a scanner. If you don't have the necessary equipment for a particular step, go on to the next one.

For further information, or to share your findings, please visit us at

Want to help? Download test sheets at
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Step 1: Print a page with text/graphics

Picture of Print a page with text/graphics

Print out a page from a color laser printer. The page should use color and have some text or graphics on it. You can find a list of printers that we know print tracking dots at our website.

As you're looking for the dots, keep in mind that they're printed in a regularly repeating pattern across the entire page (not just in the corner of the page), and will be intermixed with other printed data.

calmlunch3 days ago


spewlocks5 days ago


clapfilk17 days ago



Its nice

Thats hip

bearblue1 month ago


bearblue1 month ago


gazumpglue2 months ago

Very weird and strange.

Mariska Botha7 months ago
Very weird and strange.
BunnyRoger7 months ago
Scary facts.
This is wrong in so many ways and quite disturbing as well come to think of it...
MAApleton7 months ago
I find this just a tiny bit silly, or it it just me?
jillef8 months ago
What about scanned documents? If a document if scanned from any scanner and then saved as a jpeg and sent as an email where the IP cannot be tracked is there any data that can be found then on those jpegs?
Thank you so much :) You made my day !!
heckstallw1 year ago
Its usful
rickafost1 year ago
sensational and informative
Why is that one guy wearing a lab coat and safty goggles? Is printing really that dangorous? What a joke!!
LOL he looks Like Harold Ramis from Ghost Busters !
itsme1234 years ago
why could not you just print a blank page many times thru different printers ( or print in white something like a period). running it thru top first , then bottom first then thru other printers, it would be hard to tell which printer made which mark making it hard to tell exactly where each mark came from
vov35 itsme1232 years ago
It's impractical to do so on a regular basis to help prevent being spied upon, but yes, this would cause problems with their system. Congratulations, now the system is only useful for invading our privacy and not preventing fraud. :D
"It's outrageous that manufacturers make secret deals to compromise our privacy." What privacy? How many times do you send a letter to some one and you do not want them to know who sent it? This is not any different than your IP address being included in an email or saved at a website.
when you print something you expect it to be anonymous unless you intentionally signed it for love letter (do you really want it to be anonymous ?) you probably just print and its anonymous. for some other stuff you may want to use a generic font / shred the text with babelfish / handle the page with gloves. you sure dont want the dots there
The dot's don't identify the person, right? Just the printer. Then this has nothing to do with privacy. The dots will only tell someone that a XXXprinter printed it, not Bob Smith printed it.
scenario 1 your boss asked you to print some stuff for him with deadline. deadline passed and you did not do that. boss calls and asks whyits not ready. you tell him you sent and thats the mail service fault (and not yours). you sit to print it and remember to write there the date of 2 days ago (to make the show perfect) boss recieves the mail. he is freaked off how late the docs arrived and shares his rage with a friend. his friend suggests him to check the true date encoded in the dots and decode that using the calculator in the EFF site scenario 2 you are a journalist who uses the computer for his professional stuff as well as his personal stuff. he prints a doccument that he wants to make confidential so that no one can get on him if the document falls in the wrong hands. the document does a month ago his daughter married an he printed the invitation letters on the same printer. one of those letters is enough to link him to the confidential doc via the printer serial number the dots contain information that you did not intend to include in the document you print and you are likely to be unaware of its existence. this is a privacy issue. no need in your name it may be very complicated to find by incident a titled document printed on the same printer - so it does not look that severe. possibilities become huge when dots meet other info that can be esily crossed with them - like where was batch of printers of model X and manufacture date Y sold - probably available from the manufacturer lets wait for the EFF guy to explain more
Cereleste, you are correct, the information is just Lexmark - serial number xxxx-xxxxx-xxxxxx and perhaps the date and time. This is not printing out your name, address, and contact information. 11010010110: Both Scenarios are possible, but not really probable. Unless that Boss makes it a policy to look at the dots on each page, then he probably would not even think about it. If someone is using a printer for both "questionable" business practices and personal use, he deserves to be caught. Base line point is this: If you are printing something out that you do not want to be linked to in any way what so ever, make sure you have an older printer that does not support the dot printing.
Post Script: This is nothing new. Forensic Detectives used to be able to tell what typewriter was used to create a letter based on the pits in the letters as they stamped into the ribbon and paper. Some companies would even put these pits into their letters on purpose so that it was a form of signature that their typewriter was used.
You do realize there are other ways to tell where a document came from... Forensic scientists and the FBI don't need fancy dots to tell them where a document came from. And if every model has a different method of placing dots, it would take more money and time to develop a database of different methods and then cross check the dots with the database. I don't believe it's worth it. And i guarantee I'll get a scathing reply about "the man" and how "big-brother" is watching, but i still believe that this is the printer manufacturers decision and not the government violating your freedom of speech.
But such a database would connect a document to a model of printer, not to an individual printer, as the coded dots do. Nothing to do with big brother watching or free speech. The USA darn nearly descended into McCarthyism, with no respect for the bill of rights, post 9/11. No need to give the government more tools to harass anyone that doesn't tow the nationalists line.
vov35 static2 years ago
most high value electronics have a unique serial number. they can identify the specific printer that this came from.
The government doesn't harass those that don't "tow
not  true the fbi created the method... i fix copiers.  no color copier is allowed to be sold in the usa without this dot pattern encoded in the image it is created in the print engine not from the image process even when the machine is internaly calibrating itself these dots are formed and visable  on the transfer belt  the only information encoded  in the dots is model numbers and time and date that way if a faudulent document is found it can be traced back to the source day the fbi showed up and took an entire machine as evidence when some funny money showed up...BTW most high end color copiers can detect money being prited on them and will actually code to the point where your local rep cant fix it and a rep from the manufacturer has to come in and reset it  ...that how deep the rabbit hole goes my friend  for the manufacture i represent there are only 4 people in the usa that can reset that code
Then why ask the printer companies to institute the yellow dots, if they don't need them? And if they asked them to include this technology, then don't you think they maintain a comprehensive database of what the dots mean? It's not like Xerox/XP/Canon etc. has a vested interest in what you print.
i think the effort it would take to maintain a database of yellow dot patterns outweighs the benefit. To answer your question, no i don't think the government maintains a database of yellow dot patterns, and Xerox, HP, Canon, Brother DO have a vested interest in what you print, or rather how you print.
You are correct, this is not something that the government has in created, it is only a digital signature of the printer. Now if someone were to say print off a threating letter and send it to someone, then this could be used to help track the person in question down. But just by looking at the dots on the page would not be all that it takes.
my point exactly.
Comparing apples to oranges. The detectives have to have both the document and typewriter in hand to connect the document to a typewriter, and the typewriter to an user. Same goes for using old school methods used to match a document to a printer. Now only the document is the only thing needed to connect it to a specific printer.

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