Short explanations of ZPL, written from what the renderer actually does, not from what the documentation says it should.
ZPL is the language Zebra thermal printers speak. The file is not a picture of the label: it is the recipe for drawing one, which is why it opens in Notepad and opens nowhere else.
ZPLAn address with ç or ã prints as a box and a stray symbol. The cause is one missing line in the file, and the fix is five characters long.
AccentsYou asked for three copies and got one. You declared the size in the file and it made no difference. Neither is a fault: these are commands that only exist for a printer, and converting is not printing.
Printer commandsZebra's manual lists over two hundred commands. A shipping label uses fewer than twenty. This is that list, with what each one does and the mistake each one tends to cause.
ReferenceThe three barcodes that turn up on shipping labels, the command that sets bar width, and the two reasons a barcode looks perfect in the PDF and fails at the scanner.
BarcodesNot every label file is ZPL. It might be EPL, a PDF with the wrong extension, or a JSON with the ZPL hidden inside. Each one gives itself away in the first line.
ZPL and EPLZPL does not wrap text on its own. Anything that does not fit the width runs off the edge and disappears. The command that fixes it is one letter away from the one everybody uses.
Line wrappingLarge batches are where most converters give up: the tab freezes or memory runs out. How a file of hundreds of labels is processed here, and what to do when it goes over the limit.
Large batchesWith no thermal printer, you can print on a plain sheet and stick it on. There is exactly one setting that has to be right, and it is the one that comes wrong by default.
Printing^FW looks like the rotation command and is ignored on conversion. What actually rotates is the letter inside ^A0, and not knowing the difference costs an afternoon.
RotationA carrier's ZPL file is a list of other people's names, addresses and phone numbers in plain text. Understanding what you are carrying changes how you handle the file.
PrivacyThe three commonest reasons a label never reaches the PDF, two of them with no error on screen at all. How to spot each one by looking at the file, tested against the renderer EasyZPL uses.
Common errorsDensity is not a quality setting: it is a property of the file. Picking the wrong one moves everything on the label. How to find the right one in thirty seconds.
Density