According to the U.S. Bureau of Engraving and Printing, microprinting is one of the many anti-counterfeiting techniques used in currency and other financial and identity documents. A line of microprinting simply looks like a line of ink to the naked eye, but if examined under a microscope, it is revealed to be made up of tiny lettering.
Microprinting is a valuable anti-counterfeiting tool, because the printers used to create currency, checks and other secure documents are capable of this extremely detailed work, while most consumer printers and copiers are not. If someone attempts to copy an item protected by microprinting, the relatively low resolution of the scanner blurs the small letters into a single solid line in the captured image. Even if a counterfeiter obtains a high-quality scan of a microprinted document, most printer ink soaks into the paper, blurring the characters into a useless line. Examination of the document under magnification reveals this mistake, and identifies the item as a forged copy. Businesses interested in producing secure documents can purchase specialty printing hardware and software that allows them to imbed microprinting into their products, although these commercial microprinters are incapable of producing the same level of detail used in official government documents and currencies.