Many believe the "mark of the beast" will be a computer bar-code tattooed on the forehead or hand. It would be visible for quick identification, and for scanning. Using a bar-code would be possible, since the standard bar-code contains twelve numbers; that would mean there would be 100 billion numbers available, which would be no problem for there are only about seven billion people on our planet. But with the bar-code, unless the person bought or sold something, it would be difficult to track the location of that individual. Actually, the Scripture says nothing about tracking their location, but only that buying and selling would be restricted (Rev. 13:17).
While a combination of a bar-code and a micro-chip would enable the ultimate "control freak" to locate an individual, and limit his or her ability to buy or sell, proponents of both forms of identification appear to be ignoring what the Word says about the "mark of the beast." John wrote: "And that no man might buy or sell, save he that had the mark, OR the name of the beast, OR the number of his name. Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six" (Rev. 13:17-18 - emphasis mine). That means it cannot be a bar-code for scanning. Neither can it be a micro-chip.
What it could be, is a tattoo OR brand of his religious symbol (perhaps a crescent moon and star), OR his actual name, OR the number 666, OR his name represented by an alpha-numeric system that adds up to 666. Because we can now identify people by eye scans (forehead), and by their finger prints (hand), a tattoo or brand would be all that was necessary to identify those who worshipped the Beast (Rev. 13:15; 14:11; 16:2; 19:20).
While we do not know what the mark is, we do know not to worship the Beast!