Raw ZPL or zeepler?

A 3 × 1 inch asset tag: a department, a location and a Code 128 barcode of the asset number.

^XA
^PW609
^LL203
^CF0,28
^FO20,15^FDPUBLIC WORKS^FS
^CF0,24
^FO20,50^FDYARD-3^FS
^BY2,2,59
^FO20,85^BCN,,N,N,N,A^FDAST-88213^FS
^XZ

• ^PW609 and ^LL203 set the label to 3 × 1 inches at 203 dpi.
• ^CF sets the font for the fields after it, and ^FO places each one, in dots from the top-left corner.
• ^BY sets the barcode's module width and height, and ^BC prints the Code 128 barcode.

To print a different asset, your code puts new values between ^FD and ^FS. That is where most of the work turns out to be: a value with a ^ or ~ in it is read as a command, and a value that is too long runs off the label without an error.

Send this body to POST https://api.zeepler.com/v1/zeeplify with your API key in the x-api-key header. It is a working request, not an illustration: on every change, our tests run this same file through the API's code and compare the result with the ZPL below.

1{
2  "config": {
3    "size": "3x1"
4  },
5  "data": {
6    "asset": "AST-88213",
7    "dept": "PUBLIC WORKS",
8    "location": "YARD-3"
9  },
10  "templates": [
11    {
12      "type": "Text",
13      "dataPath": "dept",
14      "coords": [20, 15],
15      "font": "0,28",
16      "maxLength": 20
17    },
18    {
19      "type": "Text",
20      "dataPath": "location",
21      "coords": [20, 50],
22      "font": "0,24"
23    },
24    {
25      "type": "BarCode",
26      "dataPath": "asset",
27      "coords": [20, 85],
28      "style": "code128"
29    }
30  ]
31}

And the ZPL that comes back, ready to send to the printer:

^XA^MCY^XZ
    ^XA
    ^SZ2
    ^MMT
    ^MNY
    ^LL203
    ^PW609
    ^LH0,0
^CF0,28^FO20,15^FDPUBLIC WORKS^FS
^CF0,24^FO20,50^FDYARD-3^FS
^BY2,2,59^FO20,85^BCN,,N,N,N,A^FDAST-88213^FS
^XZ

The layout and the data are separate, so the same body works for every asset. zeepler escapes ^, ~ and _ in the data, cuts text at maxLength when you set it, and refuses a body with a field that starts outside the label, naming the field, before anything reaches a printer. A field that starts inside and runs past the edge is still yours to catch, as it is in raw ZPL.

• Your labels rarely change, and someone on the team already knows ZPL. A fixed label with a few values swapped in is a short template, and it costs nothing per label.
• You need a command zeepler does not have yet. It makes text, Code 128, Code 93, EAN-13 and QR codes on 3 × 1 and 4 × 2 inch labels at 203 dpi. Wrapped text (^FB), boxes and lines (^GB), images (^GF), rotation and 300 dpi printers all mean writing ZPL yourself, for now.
• The printer cannot reach the internet, or the data must not leave your network. zeepler is an API: each label is one HTTPS call.
• You print in volume at high speed and want no network call in the path. Generating ZPL in your own code takes no round trip.

• The data lives in your system, and you would rather send it as JSON than maintain ZPL strings.
• The values come from people or other systems, so escaping and length limits matter.
• You want a mistake caught before it prints: every problem with a request comes back in one 400, each with the path of the field.
• Several systems or teams print the same label, and you want one definition of it.

• zeepler and Labelary: Labelary turns ZPL into images; zeepler turns your data into ZPL. What each does, and when you would use both.