Step 2: Blue light (w/ unaided eye) method

You'll need a blue light for this method. EFF has blue LED lights available, or you can get a blue LED flashlight or any other strong blue light from any other source. An ordinary battery-powered blue LED will work.

Turn off all the lights, and eliminate as much ambient light as possible. Shine a blue LED light on the blank part of the printed page. As examining a printer page under blue light improves the contrast, the yellow dots should appear black.

If you have good close-range vision, you should then be able to see them easily. They might initially look like small flecks of dirt or dust. If you can't see the dots this way, check to be sure that your printer is known to produce them, and try asking a friend to have a look.
What about B/W laser printers.
<p>I saw on a CSI-like program they said printers put a unique code on the sheet, the prop that they used (from a B&amp;W printer) had a tiny line nearer to a corner of the sheet. i looked for such a line on my prints but never found it... so maybe they do, maybe they dont, either that or the B&amp;W printer has a high DPI so that the dots over the sheet are too small, or maybe the dots are now encoded into the way the printer renders shades of grey/colour (called dithering) - which might be present on printers you have previously thought were OK.</p>
<p>Geez man, thanks for the reply, but my above comment is 7 years old, I even forgot what instructables was.</p>
<p>So, for simple text, wouldn't printing with a yellow background obscure the code to the point that it couldn't be detected?</p>
It's the illuminati, I told them, they never listened. I also don't trust toasters, they probably put crazy tracking sh*t in them too.
<p>what's with all the bots here? their accounts advertise insurance and cruise websites. they are the ones with single word comments and comment the same stuff on other 'ibles.</p>
<p>this is like the NSA spying on our phone conversations</p>
<p>Thats sweet</p>
<p>his is wrong in so many ways and quite disturbing as well come to think of it...</p>
<p>Its fabulous :)</p>
<p>Its nice</p>
<p><br>Thats astounding<br></p>
<p>Thats cold</p>
<p><br>Its extraordinary</p>
<p><br>Thats magnificent...<br></p>
<p>Its nice</p>
<p><br>Thats hip<br></p>
<p>Very weird and strange.</p>

About This Instructable




Bio: We are an international non-profit advocacy and legal organization dedicated to preserving the right to freedom of speech in the context of today's digital ... More »
More by EFForg:Yellow Dots of Mystery: Is Your Printer Spying on You? 
Add instructable to: