Code 128 Barcode Generator

Code 128 packs every ASCII character into a compact linear barcode, which is why it appears on shipping labels, inventory and asset tags and lab samples. This generator picks the shortest mix of code sets automatically or lets you force 128A, 128B or 128C, and it builds GS1-128 (formerly UCC/EAN-128) labels from AI syntax, checking lengths, characters and check digits. The barcode is drawn in your browser.

How to use this tool

1. Enter the data. For GS1-128, write each Application Identifier in brackets, e.g. (01)09506000134352(17)261231(10)ABC123.
2. Choose the mode — Auto gives the shortest barcode for almost any data.
3. Set the bar (module) width, the bar height and whether the text is printed.
4. Download a PNG for labels and screens, or an SVG for print artwork.

Formula

check value = (start value + Σ position × character value) mod 103 · width = 11 × characters + 2 modules

Every symbol character is 11 modules wide and the stop pattern 13, so a symbol with n characters (start, data, check and stop) is 11n + 2 modules, plus a quiet zone of at least 10 modules on each side. Set C stores two digits per character, so runs of four or more digits are switched into C. A GS1-128 symbol starts with FNC1, and an FNC1 separator follows every variable-length field except the last; predefined-length AIs such as (01), (11)–(17) and (31nn) need none.

Example

ABC-123456 in Auto mode starts in set B for “ABC-”, switches to set C and stores 12, 34 and 56 as three characters: start + 4 + Code C + 3 + check + stop = 11 characters, 123 modules wide (143 with quiet zones), or 246 px of bars at 2 px per module. In GS1 mode, (01)09506000134352(17)261231 — GS1’s sample GTIN with an expiry date of 31 December 2026 — is 24 digits that all fit set C: start, FNC1, 12 digit pairs, check and stop make 16 characters.