Stacked codes are two-dimensional bar codes. As the name indicates, they are stacked one-dimensional barcodes, where several barcodes are placed on top of each other in rows. Since stacked codes contain information in both axes, they belong to 2D codes.
With stacked codes, multiple bar codes such as Code 39 and Code 128 are stacked on top of each other, which means stacked codes have a higher information density and can store larger amounts of data without errors. Depending on the stack code, they can have between two and up to fifty lines and between one hundred and about three thousand characters.
The actual information is located in the X-axis and can be read out line by line. Each line is recognized by start and stop characters and is equipped with check characters. Barcode readers with minimal modifications can be used as barcode readers. Moreover, the code groups can work with the decoding routines of the bar code readers.
Known stacked codes are PDF417, Code 49, Code 16K and Codablock.