Quick answer: enter the digits, choose the check-digit method your scanner or software uses – Mod 10 is the most common – and download. Because MSI has no standard check method, matching the setting on your scanners is what matters.
Why MSI is still on supermarket shelves
MSI Data Corporation modified the Plessey code in the 1970s for its handheld ordering terminals. Grocery chains adopted those terminals to scan shelf-edge labels when re-ordering stock, and the format stayed. You find MSI on shelf tags, warehouse bin locations and old inventory systems – rarely on products.
| Check option | What it adds |
|---|---|
| Mod 10 | One Luhn-style check digit – the most common |
| Mod 10 + Mod 10 | Two digits, the second calculated over the number plus the first |
| Mod 11 | One check digit with weights 2–7 |
| Mod 11 + Mod 10 | Mod 11 followed by Mod 10 |
How to create an MSI Plessey barcode
- Enter the number. MSI encodes digits only.
- Choose the check digit. Mod 10 is typical; Mod 10/10 adds a second Mod 10 for extra safety. Some systems use Mod 11.
- Download. PNG for single labels, PDF label sheets for a full set of shelf-edge tags.
- Test with your scanner. MSI is not read by phone apps or our scan test – try one label on your actual handheld before printing hundreds.
A word of caution
MSI has no start/stop protection against partial reads and the check digit is the only safety net, so always use one. Most handheld scanners support MSI but ship with it switched off – enable it in the scanner's configuration (usually by scanning a setup barcode from the manual) and set the same check method as here.
Printing shelf-edge labels
Shelf labels are usually printed many at a time on perforated sheets or rolls. Paste all the location or item numbers into the bulk box, one per line, and download the printable PDF: the barcodes are arranged in a grid on A4 or US Letter at their real size, ready for label sheets or for cutting. For narrow shelf strips, reduce the bar height in “Customize design” – MSI stays readable with a short height as long as the bars are sharp.
MSI and the original Plessey code
The Plessey company in the UK created the original code in 1971 for library and stock systems. MSI simplified it: each digit is four bits, written as four bar-space pairs where a wide bar means 1 and a narrow bar means 0. The result is easy to print but has no protection of its own, which is why the check digit choice above matters so much.
Frequently asked questions
Why can’t phone apps read my MSI barcode?
Most phone scanning libraries do not support MSI. Dedicated handheld scanners do, once MSI is enabled.
Which check digit should I choose?
The one your scanner and software are set to verify. If unsure, look at an existing label: a scanner set to “transmit check digit” shows it at the end.
Is MSI the same as Plessey?
MSI is a modified version of the original Plessey code. Plessey UK can be made in the main barcode generator.
Can MSI encode letters?
No, only digits 0–9.
How long can an MSI barcode be?
There is no fixed limit, but shelf labels typically use 6–12 digits. Longer numbers make the barcode very wide because MSI is not a dense code.