Code 128 barcode generator
Encodes any ASCII text at any length, and is the usual choice for shipping labels, asset tags and anything internal where the number is yours to define.
How to make a code 128 barcode
The density is what makes it the default for logistics: Code 128 has a mode that packs two digits into each symbol, so a long numeric serial takes about half the width it would in Code 39. It also carries a mandatory checksum, which Code 39 does not, so misreads are caught rather than silently accepted. The practical caution is width. A long value produces a very wide barcode, and the fix is almost never to shrink it horizontally, which destroys the bar ratios. Either shorten the data or accept the width. GS1-128 is the same symbology with a standardised data structure layered on top for supply-chain use.
Questions
Any ASCII character, at any length. That flexibility is why logistics uses it.
It has a mode packing two digits per symbol, so numeric data takes about half the width.
Yes, a mandatory checksum, calculated automatically. Code 39 has none.
Almost always resolution or contrast. Print from the SVG rather than scaling a PNG, keep the quiet zone clear on both sides, and use black on white; a coloured or shiny background defeats most scanners.
Not by scaling, that breaks the bar ratios and it stops scanning. Shorten the data instead.