Product Line Card
Fundamentals of PDF417 Symbology
The advent of PDF417, a 2D stacked linear code,
brought two important changes to the barcode industry.
First, it provided a method of greatly increasing data
capacity in a label. Second, through built-in error
correction, it provided a way to ensure that the added
information could be accurately decoded.
“PDF” stands for portable data file, aptly named as
the symbology can hold (in a reasonable amount of
space) a maximum of 1,850 ASCII characters and 2,710
numeric digits, enough to encode an entire database.
This far exceeds the data capacity of any linear code.
Because of this limitation, linear codes force the user to
rely on external database lookups to provide complete
information on the stored data. Conversely, PDF417
provides the ability to carry all the information with the
code, particularly beneficial to open systems.
PDF417 uses a technique that stacks multiple linear
rows together which dramatically increases the amount
of data that can be encoded compared to linear
symbologies. Every PDF417 label has distinct elements,
including start/stop patterms, left/right row indicators,
data columns, and rows. PDF417 can be scanned
by linear scanners, raster laser scanners, or two-
dimensional imaging devices.
The Importance of Reed-Solomon Error Correction
Using Reed-Solomon error correction, up to 50
percent of the label can be damaged or torn while still
The user selects the degree of error correction for the
label at the time the label is created. Levels range from
level 0 to level 8, with level 8 being the most redundant.
Error correction identifies two types of errors: 1) rejection
errors, called “erasures,” and 2) substitution errors,
called “errors.” An erasure is a missing, unscanned, or
undecodable symbol character where the position of the
symbol character is known but not its value. An error
is a misdecoded or mislocated symbol character where
both the position and value of the symbol character is
This PDF417 label has 250 alphanumeric
By stacking linear codes,
PDF417 provides in-
creased data capacity.