What is the difference between MSI and Plessey?

MSI is a variant of the original Plessey code, refined by MSI Data Corporation. In practice almost every scanner that mentions Plessey support means MSI.

Can MSI encode letters?

No. MSI is strictly numeric. Use Code 39 or Code 128 if you need letters.

Does MSI need a check digit?

Check digits are optional and several schemes exist, including mod 10 and mod 11. Add the digit to your value if your system expects a particular scheme.

Can I use MSI at checkout?

No. Retail point of sale requires UPC-A or EAN-13. MSI is for internal shelf and inventory labelling.

Which check digit scheme should I use?

Modulo-10 is the common default. Modulo-11 and double check digits exist but must match whatever your scanners expect.

Is MSI the same as Modified Plessey?

Yes. MSI, MSI Plessey and Modified Plessey all describe the same symbology.

Can I use MSI on retail products?

No. Retail requires GS1 symbologies. MSI stays inside your own operation.

Why does my MSI barcode look longer than a Code 128 with the same digits?

It is. MSI encodes each digit in a fixed four-bar pattern, so density is much lower than Code 128 subset C.

Barcode generator / MSI Plessey

MSI Plessey Barcode Generator

Generate MSI (Modified Plessey) barcodes free online for inventory and shelf labels. Numeric input, PNG and SVG download, no signup and no watermark.

Barcode data

Digits 0-9 only, any length.

Bar height80px

Show number under barcode

PNG resolution Pro

Preview

No watermark, no signup, unlimited PNG downloads. Rendered in your browser — the value you type never leaves your device. Vector SVG and high-resolution PNG are included with Pro.

What is MSI Plessey used for?

MSI, also called Modified Plessey, is a numeric-only symbology built for shelf-edge labels and warehouse inventory tags. It is variable length and continuous, and it is still used for supermarket shelf tagging and internal stock control in retail back offices.

MSI is not intended for point-of-sale scanning and carries no product identity beyond whatever number you assign it. Choose it for internal numeric references where the scanning hardware is already configured for MSI; otherwise Code 128 encodes the same data more compactly.

Supermarket shelf-edge labels
Warehouse inventory tags
Internal stock control references

MSI Plessey specification

Character set	Digits 0-9 only
Length	Variable
Check digit	Optional modulo-10 or modulo-11
Self-checking	No — a check digit is recommended
Density	Low; wider than Code 128 for the same digits
Quiet zone	10 modules either side
Best for	Shelf-edge labels and warehouse inventory control

How to generate a MSI Plessey barcode

1
Enter the numeric location or item code used by your inventory system.
2
Append a modulo-10 check digit if your scanners are configured to validate one.
3
Increase bar height for shelf labels scanned from a distance or at an angle.
4
Download SVG for label sheets, PNG for quick reprints.
5
Verify one printed label decodes to the exact digits before printing an aisle.

Troubleshooting scan failures

Scanner does not decode MSI at all

MSI Plessey is disabled by default on many scanners. Enable the symbology in the reader's configuration before assuming the label is wrong.

Occasional wrong digits

MSI is not self-checking. Add a check digit and configure the reader to validate it.

Symbol too wide for a shelf tag

Shorten the code or switch to Code 128, which encodes the same digits far more compactly.

Letters rejected

MSI is numeric only by design.

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