Type any text, numbers or symbols to get a Code 128 barcode. The checksum is added automatically, and runs of digits are packed two per character to keep the barcode short.
Code 128 is the usual choice for barcodes you use yourself: inventory and asset tags, bin locations, order and shipping references, library and lab labels. It can hold upper and lower case letters, digits and punctuation, and it's denser than Code 39, so the same value makes a shorter barcode.
It has three character sets. Set B covers ordinary text; set C packs pairs of digits into one character. This generator picks the sets for you and switches to set C for long digit runs, which is why a long number stays compact. A mod-103 checksum is always added inside the barcode; it isn't shown in the text underneath.
This page makes plain Code 128 from printable characters (letters, digits, space and standard punctuation). It does not make GS1-128 barcodes with application identifiers such as (01) or (10), which some retailers require on shipping labels.