Create one barcode image from text you provide, using Code 128 by default or standard Code 39 when its restricted character set fits the job. Free barcode generator, barcode maker, Code 128, and Code 39 intent consolidate here.
The bundled JsBarcode 3.12.3 encoder selects valid Code 128 code sets and writes the start code, encoded data, modulo-103 checksum, and stop pattern. Standard Code 39 includes start and stop characters and uses the standard narrow/wide symbol patterns; optional Mod 43 is not applied.
Worked example
Code 128 can encode printable ASCII such as Shipment 128-A. Code 39 accepts A–Z, digits, spaces, and - . $ / + %. Lowercase Code 39 input is visibly normalized to uppercase.
Behavior and limits
Code 128 accepts printable ASCII from space through ~ and is limited to 120 characters for practical output width.
Code 39 accepts its standard uppercase repertoire and is limited to 80 characters.
Every output includes at least ten quiet-zone modules on each side; larger values are available.
Scanner success still depends on physical size, contrast, print quality, damage, and scanner support.
Common mistakes
Cropping quiet zones from the downloaded image
Printing a wide barcode too small
Assuming Code 39 accepts arbitrary lowercase or punctuation
Treating a browser image as certified packaging artwork
Encoder and standards scope
The locally bundled JsBarcode 3.12.3 encoder implements Code 128 and standard Code 39. Independent ZXing-C++ scan tests verify rendered symbols rather than trusting the production encoder alone. This is not GS1-128, a retail identifier allocator, or certified packaging artwork.
Output dimensions and quiet zones
SVG is the vector master; PNG is rendered from that current SVG at its configured pixel dimensions. The preview scales to its container without changing the download. Black bars on white are fixed for reliable contrast. Broad symbols require at least ten quiet-zone modules; UPC-A uses eleven in this tool. No arbitrary size is claimed universally scanner-safe.