PLANET (Postal Alpha Numeric Encoding Technique) is a bar code symbology used by the United States Postal Service. Unlike the POSTNET codes used concurrently with it, it allows for tracking information for individual mail pieces, where POSTNET merely encoded routing information for the destination address. These formats, however, have been superseded by the Intelligent Mail barcode, which encodes both routing and tracking information.
Like POSTNET, PLANET bars are distinguished by their length, either full or half, rather than thickness or spacing as in other bar code formats. Digits are encoded by combinations of these bar lengths. What is encoded is a Confirm subscriber ID and up to 6 additional digits supplied by the subscriber (mailer) to identify either individual pieces or entire campaigns. Full bars appear at either end of the code as a "guard rail" or "frame bar", and there is one checksum digit.