MSI Barcode Generator for Warehouse Bins and Stock Control

Where MSI still earns its place

MSI is often written Plessey/MSI, after the two companies that shaped it, and it grew out of warehouse bin and stock control in the 1970s. The brief was narrow and practical: print a number cheaply on a label applicator and read it back with a wand or an early CCD. The answer was a bar-only symbology in which each digit becomes four bar-and-gap pairs, read most-significant-bit first: a 1 is a wide bar with a narrow gap, a 0 a narrow bar with a wide gap. The gap only mirrors the bar in front of it, so no separate information rides in the spaces. The symbol is opened by a single wide start bar and closed by a narrow bar, a wide gap and one more narrow bar.

Nearly all of that work stayed inside buildings. You will still find MSI on picking locations, bin labels, pallet tickets and stock-count tags, and you will rarely find it on anything that leaves the site. Its value today is that it is easy to print forgivingly and easy for an old reader to interpret - not that it carries meaning anyone outside your operation can use.

That inward focus is also the honest caveat. A symbology with no registered authority behind it has no arbiter for sizing, no published artwork tables and no guarantee that the next scanner your company buys supports it at all. MSI keeps working where one team owns the label, the printer and the reader configuration; the moment any of those three belongs to somebody else, a documented format is the safer bet.

The check digit you are actually getting

MSI is unusual in that its checksum is not one rule but several. The same digits can be printed bare, with a single modulo-10 character, with a single modulo-11 character, with two modulo-10 characters, or with a modulo-11 followed by a modulo-10 over that result. A label made under one convention and read by a scanner configured for another is rejected outright, and neither side has done anything wrong.

This page renders MSI10: it computes one modulo-10 check digit from what you type and appends it to the symbol and to the number printed beneath it. There is no selector for MSI11, MSI1010 or MSI1110 on this site and no switch to suppress the digit that is added. If your scanner specification names one of those instead, ask your label software or reader vendor whether the checksum can be applied at the reader end, or standardise your tickets on MSI10 and set the readers to match.

MSI beside the other numeric formats

Choosing between these three is rarely a matter of taste; the existing reader firmware decides. MSI support is optional on many scanners and switched off by default on some newer hardware, so test one label before ordering a roll of tickets. Codabar and Interleaved 2 of 5 are both covered on this site if the specification points elsewhere.

Printing tickets that read back first time

Because the element pattern itself offers no error detection, the appended check digit is doing all the work: get the variant right and a bad print becomes a rejection rather than a wrong location number on a handheld in the aisle. Start from the X-dimension, the narrowest element in the symbol, and scale everything else from it, since the ability of a reader to tell wide from narrow depends on that one measurement.

• A location code prints noticeably wider in MSI than the same digits in an interleaved format, because MSI pays for its own gaps; measure the ticket before you commit to a digit field length.
• Keep clear unprinted space at both ends; the margin control supplies background, but the reader specification governs the amount needed.
• Leave the human-readable number on the label - torn tickets get keyed, and here that line includes the added check digit.
• Enable MSI in the scanner and set its accepted length to data plus one, which is the figure most people miss.