There is no hidden 666 in barcodes

 I found this image in a flat earth group

I deal with barcodes at my job, and while this particular code, UPC-A isn't one that we use there, I took a look at the UPC specification to see how accurate the claim is.

Let's start with what they almost got correct.  The areas in red are called guard patterns, so they get partial credit for "guard bars", and the blue area does encode the character six. 

However, spaces are also part of UPC patterns and symbols, and while the guard patterns at the edge consist only of a single-width bar, a single-width space, and another single-width bar, the center guard pattern also includes another single-width space on each side, and the character six is followed by a quadruple-width space.  So if the side guard patterns are 101, as they said, the center guard pattern is 01010 and that six is 1010000.

And that's only how a six looks on the right side of the barcode, all digits have a different encoding on the left or right side, if a six appears on the left side, it's a single-width space, a single-width bar, a single-width space, and a quadruple-width bar, or 0101111. Here's a barcode where all the characters are six (except for the last, which is a check-digit and is automatically computed) in which it's easy to see that sixes look different on the left side.