Code 39 Barcode Generator

What a Code 39 barcode can hold

Code 39 is a linear symbology in which each character is built from nine elements, three of them wide. A start and stop character frames every value, and the scanner adds them automatically. The character set is small: A to Z, 0 to 9, the space, and the hyphen, full stop, dollar sign, slash, plus and percent signs. That limited set is the main trade-off against Code 128.

This generator accepts up to 40 characters from that set and rejects everything else with a message that lists the allowed characters. Code 39 is the one symbology here that changes your input, because lowercase letters become capitals before anything is drawn. A value typed as lot-a7 is encoded as LOT-A7, so check the uppercase result in the preview.

The generator does not add a check character to Code 39. Some systems expect an optional modulo 43 check character, and in that case the value you type is not the one they verify. Confirm with the system that reads the labels whether it needs one before you print.

Code 39 is long established, so you will often meet it alongside newer readers and cameras. Test the label with the readers actually used on site rather than with a phone alone, since an older laser reader with a narrow window may need a larger Size to decode the bars reliably.

How to make a Code 39 barcode in three steps

1. 01

   Pick Code 39 and enter the value

   Choose Code 39 from the Type list, or press Use an example to load the sample CODE-39 SAMPLE. In the Value field, type capitals, digits, spaces and the allowed symbols. The hint under the field lists them.

2. 02

   Adjust the colors and the bar dimensions

   Set Bar color and Background, then Size for the width of each narrow element and Bar height for the length of the bars. Keep Show the number on, since the printed text is what people read when a scanner fails.

3. 03

   Preview, scan and download

   Scan the preview at print size with the reader your site uses. Download SVG to send to a print shop, or PNG, JPG or WEBP for screens and documents.

Where Code 39 is still in use

• Industrial and maintenance tags

  Machine IDs, valve tags and maintenance cards often carry a short code such as PUMP-204. Code 39 handles letters, digits and hyphens without any special setup.

• Older inventory and asset systems

  If a system already reads Code 39, a new label in the same symbology needs no change to the scanners. That is the main reason it survives in workplaces that were set up years ago.

• Public-sector and defense supply processes

  Some public-sector and defense supply processes have used Code 39 for a long time, so new labels may need to match a format that already exists in those records.

• Archive boxes and file references

  Archive boxes often combine letters, digits and a slash, such as BOX/2019/07. Code 39 keeps the slash, so the reference reads the same on the box and in the catalogue.

• Workshop and shop-floor jobs

  A job card with a code such as JOB-4471 lets a worker scan it at each station instead of typing the number into a terminal.

Tips for Code 39 labels that scan cleanly

Mind the 40 character limit

The generator stops at 40 characters, half the length allowed for Code 128. For longer references, split the value across two labels or choose a symbology that fits the data.

Check the punctuation

Only space, hyphen, full stop, dollar, slash, plus and percent are allowed as symbols. An underscore or an at sign is refused, so replace those characters before you type the value.

Keep the edges clear

Leave clear space on both sides of the bars on the label. The scanner looks for start and stop patterns at the edges, and text or borders placed too close can hide them.

Choose a height the scanner can use

Handheld lasers and cameras read different heights well. Use taller bars for a scanner that reads from a distance, and test at the distance the reader will really be held.

Code 39 questions