What is a Code 39 Barcode? – A Complete Guide

What is a Code 39 Barcode

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Code 39 is an established barcode symbology that has been applied in a number of industries, particularly the automotive and military sectors. 

Code 39 was developed in 1974 and was one of the first barcoding systems to represent numerical digits and alphabetical character set. The versatility of Code 39 made it highly popular, and its variation continues to be used in the US military’s Logistics Applications Of Automated Marking And Reading Symbols (LOGMARS) system today. 

In this article, we will take an in-depth look at Code 39 barcodes and explore why it’s still popular. So keep reading to find out more about Code 39 codes!

Code 39 - A Detailed Overview

Code 39 barcode

The Code 39 barcode is a type of 1-D barcode symbology used to encode full alphanumeric data. It was created by two Intermec researchers, Ray Stevens and Dr David Allais, in 1974. The barcode is also known by different names, including Alpha39, Code 3/9, Type 39, or Code 3 of 9.

Initially, Code 39 featured two wide black bars and a wide space that together could encode 39 characters, excluding the first and last symbol, giving Code 39 a total of 39 characters in data capacity. 

Today, Code 39 features 9 bars in total, with three wide and six narrow bars giving the barcode symbology a total of 43 character data capacity. 

Code 39 is the first alphanumeric barcode widely used and is usually found in non-retail sectors. Code 39 supports character encoding of upper-case letters (A–Z), numeric digits (0–9) and special characters including. 

  • Slash mark (/) 
  • Period(.)
  • Hyphen (-) 
  • Plus sign (+) 
  • Dollar sign ($) 
  • Per cent sign (%) 
  • Space symbol

The ISO/IEC 16388 standard defines the specifications for the Code 39 barcode.

How to Recognise a Code 39 Barcode?

Code 39 barcodes are composed of nine elements, which are five bars and four spaces. Of these elements, three are wide and six are narrow. 

To identify a Code 39 barcode, you can look for the start and stop character patterns. The first five bars will be identical to the last five bars of the code, in an alternating pattern of one narrow bar followed by one wide space, and then another narrow bar followed by a narrow space – this sequence is repeated twice more to form the complete pattern. 

Upon successfully identifying this pattern, you can be sure it is a Code 39 barcode.

Identifying Code 39 barcode

Why Do We Need a Code 39 Code?

Code 39 barcodes are useful in many industries, as they provide a convenient way to identify individual parts and products. These barcodes allow for efficient tracking of products throughout the entire production process. They also help ensure accuracy in inventory management and product tracking.

The aviation industry uses Code 39 barcodes to identify aeroplane parts properly. This helps ensure that only approved parts are used during maintenance procedures, reducing the risk of serious accidents.

The same type of safety assurance is seen in the medical sector, where barcode scanning helps correctly tracks patient information like medications and test results.

The US military also uses Code 39 barcodes for tracking purposes; for example, when logging items such as supplies in warehouses. This type of system greatly reduces the chances of overlooking vital items or miscounting mission resources.

Furthermore, some organisations use Code 39 barcodes as employee membership cards for security checks. This ensures that only authorised personnel have access to secure locations.

In short, Code 39 barcodes provide an efficient means of identifying different types of parts and products across a variety of industries, including aviation, medical services, defence and more.

Code 39 Barcode Anatomy

Detailed anatomy of Code 39 barcode

The Code 39 barcode is a linear, self-checking symbology comprising an array of bars and spaces. 

The structure of the Code 39 symbol consists of five major components.

  • Leading/trailing quiet zones
  • Start character
  • Data portion
  • End character
  • Intercharacter spaces (one module wide) that separate characters within the symbol

The start character is usually an asterisk [*], which signals to a barcode reader that a Code 39 symbol is being scanned. This component is not transmitted or included in any check character calculation. 

Following the start character are one or more pairs of symbol characters representing data. Symbol characters include an optional check digit for added security. 

Each symbol character pair is separated by an intercharacter space which consists of one module wide.

The final component of the structure is the stop character (also typically an asterisk [*]). The stop character signals to the barcode reader that no additional data follows after it. Like the start character, it is not transmitted or included in any check digit calculations. 

In order to ensure accurate scanning of Code 39 codes, leading and trailing ‘quiet zones’ are added before and after the start and stop characters. These ‘quiet zones’ are empty spaces around the barcode that helps distinguish the code from other printed material that may appear around it.

Variations of Code 39 Codes

Code 39 Full ASCII is an enhanced variant of the original Code 39 Barcode. It has been designed to encode not just alphanumeric characters but also the entire set of 128 ASCII characters. 

This greater range of characters gives it increased versatility and makes it more suitable for various applications where data needs to be held in a secure and easily accessible format. With its ability to store more data than traditional barcodes, Code 39 Full ASCII increases efficiency and cost-savings for businesses that need to process large amounts of data quickly and reliably.

Let’s take a look at Code 39 – Full ASCII barcode. 

Code 39 full ASCII code

Code 39 Full ASCII Code

Code 39 Full ASCII is an efficient barcoding solution for various industries due to its capability to represent all 128 ASCII characters, including punctuation, special symbols and even lowercase letters. 

Code 39 Full ASCII barcode encoding system provides various advantages over its 43-character regular counterpart. However, this comes at the cost of degraded character density, as a two-character combination represents Full ASCII characters and thus takes up more space. 

For example, the word “GOLDEN” would be encoded into the Code 39 barcode as GOLDEN, while the word “golden” would be encoded into the Code 39 Full ASCII barcode as +G+O+L+D+E+N, taking up twice as much space.

Structure of Code 39 Full ASCII Barcode

Code 39 Full ASCII barcode is also a type of 1D barcode consisting of an array of vertical bars and spaces representing numeric and alphanumeric data. It comprises nine elements for each data character it represents, including five bars and four spaces with three wide and six narrow elements.

The Code 39- Full ASCII symbol begins with a leading quiet zone, which is a clear area left blank before the start character that helps the scanner adjust its focus on the code.

The start character, usually an asterisk [*], instructs the barcode reader to begin decoding the code. The following characters are pairs of symbols representing the encoded data, including an optional checksum character. In between each character are intercharacter spaces that are one module wide to separate them within the symbol.

After all data characters have been encoded, a stop character (usually an asterisk [*]) marks the end of the barcode symbology. 

The stop character is followed by a trailing quiet zone to mark the end of the symbol.

Advantages of Code 39 Barcodes

List of six advantages of code 39 barcode

Here are some advantages of using a Code 39 barcode. 

  • It can encode all 26 alphabets of the English language and numerals, which was impossible with previous barcode symbologies.
  • Code 39 is a self-checking format code, meaning that a single print defect will not lead to the misrepresentation of characters.
  • It is much more secure than other barcodes of its time due to its high accuracy rate and data verification capabilities.
  • Code 39 is compatible with most barcode scanners in the market today. 
  • The ability to encode special symbols such as the dollar sign ($), plus sign (+) or per cent (%) makes it suitable for encoding currency values.
  • The barcode’s wide application range makes it perfect for many industries like retail, healthcare, manufacturing etc., as it can store large amounts of data.

How to Get a Code 39 Barcode?

Generating Code 39 barcodes is a straightforward, affordable and available process to anyone with a device and active internet connection. Users can easily make their own codes thanks to free and open-source online tools and a free barcode generator that can generate Code 39 barcodes. All they need to do is provide the numerical code linked to the applicable product, and the generator will create a high-quality Code 39 barcode quickly and efficiently.

Another way to create a Code 39 barcode is to use a label design and printing software such as Seagull Scintific’s BarTender Software

Seagull Scientific’s BarTender Software is a comprehensive label design and printing solution that is the go-to choice for businesses looking to streamline their barcode label printing operations. This powerful software allows users to quickly and easily generate Code 39 (regular) and Code 39 (full ASCII), enabling them to easily create labels for various applications. 

With an intuitive user interface and advanced features such as database integration, BarTender is the perfect choice for businesses looking to make their barcode printing processes faster, more efficient, and more cost-effective.

At Triton, we offer unbeatable prices on BarTender software with four on premise editions available – Starter Edition, Professional Edition, Automation Edition and Enterprise Edition and now BarTenders latest cloud offering – BarTender Cloud. Take advantage of this great deal to get the perfect edition for your needs today! 

If you’d like to learn more about our BarTender software offers, don’t hesitate to contact us through the live chat widget or by filling out a form on our website. We’ll be happy to answer any questions and help you get started right away.

Code 39 Design Rules

Barcode and label design is an essential part of your business’s success. To ensure that your barcodes and labels are accurate, effective, and compliant with industry standards, it’s important to follow certain best practices. 

The barcode width and barcode size are the two main considerations when designing a Code 39 barcode.

Barcode Width

Code 39 barcodes require a minimum width of 0.25 mm for the narrow bar (X-dimension) in order to be scannable with barcode scanners. To ensure maximum readability and compatibility, it is recommended to use a 2:1 ratio between wide and narrow elements, though 3:1 is also accepted. This allows scanners to quickly interpret the data encoded in the barcode, which can include alphanumeric characters and symbols. 

Two points about design rules of barcode width in Code 39 Barcode
Two points on design rules of barcode dimensions in Code 39 Barcode

Barcode Dimensions

The minimum recommended symbol height is 5 mm or 15% of the symbol’s width (excluding quiet zones). 

Quiet zones of a Code 39 barcode must be at least ten times wider than the current X-dimension to guarantee successful scan readings.

Our guides on Best Practices For Designing Perfect Labels And Barcodes and Common Mistakes To Avoid When Designing Barcodes offer helpful advice on creating high-quality barcodes and labels.

How to Print Code 39 Barcodes? - Barcode Printing Best Practices

Four printing rules of Code 39 Barcode

In order to ensure the successful scanning of a Code 39 barcode, there are several printing rules that you should follow.

  • Code 39 barcodes should be printed in pure black with a white background. If colour is necessary, it should be a very dark barcode font against a very light background.
  • There should be a clear white “quiet zone” around the barcode to prevent any interference and improve readability when scanned.
  • The printer settings should also be set at the highest photo quality for the best results and reliability. You can also adjust the print resolution and print speed and experiment to find the right settings that consistently produce scannable barcodes. 
  • It is beneficial to test-scan the barcodes in full sunlight or direct overhead lighting to ensure all barcode information is picked up correctly.
  • Checking for smudges, scratches, or other defects can help to prevent potential issues caused by hindering clarity and readability of the Code 39 barcode.

Thermal printers are an ideal choice for businesses wishing to print Code 39 barcodes efficiently and accurately. These printers offer cost savings, as they do not require ink or toner like other printing technologies. 

Additionally, thermal printers boast faster output speeds than other options, leading to increased productivity. Maintenance requirements are also lower, providing further cost savings in the long run.

At Triton, we offer a comprehensive selection of thermal printers from trusted brands such as Honeywell, Zebra, and TSC. We have direct thermal printers, thermal transfer printers, barcode label printers, desktop printers, and industrial printers that are designed to provide superior performance for any application. 

Additionally, we stock print consumables of the highest quality that feature outstanding adhesion and long-lasting print results. Our consumables range includes thermal transfer ribbons, thermal labels, thermal carton labels, thermal carcase tags, and food-compliant thermal inserts, which are all produced to meet the highest standards.

Our combination of excellent products backed by expert customer service makes Triton Store the best choice for businesses seeking reliable thermal printing solutions.


Code 39 is a versatile barcode symbology that has been used in many industries for decades. It provides an efficient way to encode alphanumeric data and supports encoding upper-case letters, digits or special characters. With its wide range of uses, Code 39 remains one of the most popular types of barcodes around today. 

We hope this article was useful and provided deep knowledge about Code 39 barcodes. 

Thanks for reading! 

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