Linear barcodes are uni-dimensional, i.e. the same data is present in all vertical elements. If you increase the number of characters in a linear barcode, it expands horizontally. The vertical dimension remains unchanged. Increasing the height of a linear barcode does not change its data capacity, just the ease of scanning.

The 2-D symbologies take advantage of both horizontal and vertical encodation to reduce the symbol size and achieve character densities up to 2000 characters per square inch. There are two primary approaches taken. The first is to "stack" high-density linear symbols with very small vertical measurements. The other is to use a "pattern" code in which data can be en­ coded in an X-Y matrix.