Labelproof

Every rule, and why it exists

43 checks. Each one describes a way a label can be valid ZPL and still fail — at the printer, at the scanner, or at goods-in.

Every rule cites a source.The Zebra ZPL Programming Guide, the GS1 General Specifications, and the GS1 Barcode Syntax Dictionary. Three more are written and withheld because no source confirms them.

structure5

will failST-01Zebra printer receives the label but nothing printswill failST-02One field swallows the rest of the ZPL labelwill failST-03A ^FX comment is printing text onto the labelwill failST-04Long text is cut off at the end of a ZPL fieldwill failST-05One field prints in the wrong place for no visible reason

layout6

will failLY-01Zebra label is cut off on the right-hand sidewill failLY-02The same ZPL prints differently on two Zebra printerswill failLY-03^LL is ignored and the label length is wrongwill failLY-04The tops of letters are cut off at the top of the labelwill failLY-05^LH is ignored and the label prints at the wrong originwill look wrongLY-06Every label after the first prints offset

barcode13

will failBC-01Zebra barcode prints as a thin line and will not scanwill failBC-02Barcode is clipped at the right edge and will not scanwill failBC-03Barcode at the label edge will not scanwill failBC-04Text beside a barcode stops the scanner reading itwill failBC-05GS1-128 barcode rejected for wrong bar widthwill failBC-06Barcode scans on a handheld but fails at the dockwill failBC-07Changing the ZPL barcode ratio has no visible effectwill failBC-08Code 39 barcode prints wrong or not at allwill failBC-09Code 128 barcode will not encode this datawill failBC-10UCC case-code barcode silently drops characterswill failBC-11Barcode prints as a blank space on the labelwill failBC-12A ^GB box prints as a solid black rectanglewill failFLD-C128C-ODD-001Code 128 subset C mangles an odd number of digits

state2

will failSTATE-BY-LEAK-001Barcode width changes depending on what printed beforewill look wrongPQ-01Serial numbers print as identical duplicates

gs17

will failGS-01GTIN rejected for wrong length or bad check digitwill failGS-02SSCC rejected for wrong length or bad check digitwill failGS-03GS1 expiry date rejected as invalidwill failGS-04Scanner merges two GS1 fields into onewill failGS-05Scanner reads a GS1-128 as a plain Code 128will failGS-06Scanner returns GS1 data with the brackets includedwill failGS-07GS1-128 data comes back with an extra digit on the end

data3

will failDT-01A ^ or ~ in the text breaks the rest of the labelwill failDT-02Accented characters print as mojibakewill look wrongDT-03A ^FB text block overflows instead of truncating

font1

will failFN-01Label prints in the wrong font on another printer

graphics2

will failGR-01Downloaded graphic prints as garbagewill look wrongFLD-XG-MAG-001A magnified ^XG logo looks jagged and grey

config1

will look wrongMD-01One label changes the printer settings for everyone after

portability2

will failFLD-DPI-DESIGN-001Label prints half size or double size on another printerworks, non-standardFLD-EXTREF-001Label prints blank on a printer without the stored format

coverage1

works, non-standardFLD-NOBARCODE-001No ZPL barcode found — it may be inside an image