MSI Barcode Generator

What is MSI Plessey?

MSI, sometimes called Modified Plessey, is a numeric-only symbology developed for inventory and shelf labelling. It survives in warehouse and retail back-office systems, particularly for shelf tags where the label is scanned by staff rather than at a checkout.

Check-digit schemes

MSI has no single mandated checksum. Implementations use modulo 10, modulo 11, or a pair of them, and your scanner has to be configured to match. This tool offers all the common combinations and shows the digits it appended, so you can compare against what your system expects. Modulo 11 can evaluate to 10, which cannot be printed as a single digit — when that happens the tool refuses rather than printing something wrong.

Choosing MSI at all

Be honest about whether you need it. MSI is not a GS1 standard, carries digits only, and is less dense than Code 128. If you are designing a new system, Code 128 is a better default. Use MSI when you are feeding equipment that already expects it.

Shelf-label practice

Shelf tags get handled, scuffed and re-printed often. Print with plenty of bar height so an angled scan still crosses the full symbol, keep the quiet zones, and avoid thermal paper for anything that lives under bright lights for months. The barcode label maker can lay out a full sheet at once.

Privacy

The number you type never leaves your browser — no lookup, no logging, no analytics event. That matters more than it sounds for inventory data, which is often commercially sensitive.

Limitations

Digits only, no standardised checksum, and no retail acceptance. Never use MSI where a GTIN is expected.