Fit the identifier to the receiving application
Use an existing SKU, location key or asset reference that your own records recognise. A scanner usually delivers decoded characters to software; the bars do not explain whether those characters mean a bin, an order or a product. Establish one convention before printing thousands of labels. A plain Code 128 symbol is also different from GS1-128: the latter uses FNC1 and GS1 Application Identifiers. This page does not turn arbitrary text into a compliant logistics message.
Build a traceable sample in three actions
Enter printable ASCII in Value, preserving the exact spelling and punctuation from the source. Press Create barcode to render Preview, then read back the human-readable line before using Download SVG or Download PNG. Try a representative longest identifier as well as a short example. Do not add surrounding spaces to make a code appear centred: spacing belongs in the layout, while a leading or trailing space may become meaningful data to the downstream application.
Length changes the space requirement
Code 128 width depends on the encoded characters and the selected code sets. There is no single universal millimetre width for every SKU. Let the generated quiet zones survive placement and use sufficient bar height for the scanning environment. A long mixed reference squeezed into a narrow shelf strip can produce finer elements than the printer handles reliably. Consider the identifier length and the actual dot pitch together rather than stretching the exported image to an arbitrary rectangle.
Distinguish a character problem from a print problem
This interface accepts its documented printable ASCII input; a Turkish accented character or an emoji should not be silently transliterated just to pass validation. Correct the agreed identifier convention at the source if necessary. For print failures, inspect contrast, resampling and page scaling before blaming the data. At 203/300 dpi, check a real output sample. If the reader returns the correct string but the warehouse app rejects it, investigate that application’s lookup and scanner suffix settings.
- Is Code 128 the same as GS1-128?
- No. GS1-128 adds a specific start pattern and structured GS1 fields. A general SKU barcode should not be labelled as a standards-compliant shipment label.
- Can I encode lower-case letters?
- The supported printable ASCII input includes lower-case characters. Preserve the casing your system uses; changing it can point to a different record.
- Does the visible string need an extra check digit?
- Code 128 has an internal symbol check character handled by encoding. Do not append an invented product digit to the identifier as a substitute for that mechanism.
- Why is one Code 128 much wider than another?
- Its size depends on the input sequence and encoding. Judge the final symbol at a suitable physical module size instead of comparing only character counts.