What is a Code 128?
The dense, modern linear barcode, and the one to pick when nothing forces your hand. It holds every ASCII character across three overlapping character sets, and switches between them mid-symbol - which is how it packs a run of digits two to a symbol and still manages letters and punctuation when it has to. A check character at the end catches misreads.
What it holds
Letters, digits and punctuation, anything in ASCII. There is no fixed length, but a barcode gets physically longer with every character, and a long one needs either a wide label or a scanner held close - forty characters is already a lot to ask of a shelf edge.
Making a lot of them
Drop a .txt or .csv on this page and every line becomes its own Code 128, all of them zipped together. A CSV is read from its first column. Nothing is uploaded - the codes are drawn in this page, on your machine - so a list of five thousand costs nothing and takes as long as your laptop takes.