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Code 39 Barcodes: Everything You Need to Know in 2024

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In this article, we explore what Code 39 barcode is and its unique features. We also cover the design rules and applications of this barcode. Read on to learn more.

code 39 barcode

What is a Code 39 Barcode?

Code 39, often referred to as Alpha39, Code 3 of 9, or Type 39, is a barcode symbology that can encode uppercase letters (A through Z), digits (0 through 9), and a limited selection of special characters (e.g., $, %, +, -, ., /, and space). It is one of the earliest barcode symbologies to be developed and widely used in non-retail environments because of its ability to encode a mix of characters.


For example, "GalaxyTech Innovations" might use a Code 39 barcode to label a device with the identifier "GTI-7890Z." This barcode would start and end with an asterisk (e.g., "*GTI-7890Z*"), ensuring accurate scanning and decoding by barcode readers.

barcode code 39

Key Components of Code 39 Barcodes

Here are the key components of a Code 39 barcode:

Start/Stop Characters: 

A Code 39 barcode always begins and ends with an asterisk (*) character. This is used to notify the scanner that a barcode is starting or ending.

Data Characters: 

These are the actual data elements in the barcode, which can be a combination of numbers, letters, and special characters. Code 39 can encode 43 standard characters: 26 uppercase letters (A through Z), 10 digits (0 through 9), and 7 special characters (-, ., $, /, +, %, and space).

Bars and Spaces:

The barcode itself is made up of a series of vertical bars (lines) and spaces of varying widths. Each character in Code 39 is represented by 9 elements: 5 bars and 4 spaces. Of these 9 elements, 3 are always wide, and 6 are narrow.

Inter-character Gaps: 

These are small spaces between each character in the barcode to ensure that each character is read distinctly. It's of the same width as a narrow space and provides a clear division between individual characters to aid in the decoding process.

Quiet Zone: 

This is a blank margin on either side of the barcode to ensure that it can be read without interference from surrounding graphics or text. The recommended width of the quiet zone is at least 10 times the width of the narrowest bar/space or 0.25 inches (6.35 mm), whichever is greater.

Unique Features of Code 39 Barcode

Below are some of the unique features of a Code 39 barcode:

Alphanumeric Encoding: 

Code 39 can encode the following 43 characters:

  • 26 uppercase letters (A through Z)
  • 10 digits (0 through 9)
  • 7 special characters (-, ., $, /, +, %, and space)

Start/Stop Characters: 

Code 39 uses the asterisk (*) as both the start and stop delimiter. This makes it easy to identify and read by barcode scanners.

Variable Length: 

Unlike some barcode symbologies that have a fixed length, Code 39 barcodes can be of variable length. This makes it versatile for a variety of applications.


Code 39 is considered a "self-checking" barcode, meaning that a single print defect will not turn one valid character into another valid character.

No Built-in Error Checking: 

Unlike some other barcodes, Code 39 does not have a built-in checksum. However, a modulo 43 checksum can be added if required for certain applications.


Code 39 is a relatively low-density barcode. This means it requires more space than some other barcode symbologies to represent the same data. However, it's often chosen for its simplicity and versatility.

Wide-to-Narrow Ratio: 

The width of the bars in a Code 39 barcode can vary, but there's a specific ratio between wide and narrow bars that must be maintained. Typically, the ratio is set between 2:1 and 3:1, where the width of a wide bar is 2 to 3 times the width of a narrow bar.


The extended version of Code 39 (known as "Full ASCII Code 39") can encode all 128 ASCII characters for greater flexibility.

Benefits of Using Code 39 Barcode

Code 39 barcodes offer several benefits, and we will explore some of them below:


Code 39 is uniquely equipped to encode both letters and numbers. This flexibility makes it ideal for a multitude of applications, from industrial labeling to asset tracking.

High Readability: 

This barcode symbology is recognized by a vast majority of barcode scanners. The high contrast between its bars and spaces ensures it can be scanned quickly and accurately even in less-than-ideal conditions.

Wide Acceptance: 

Code 39 has become a foundational standard, particularly in governmental and non-retail sectors. This broad acceptance means that businesses adopting it can expect wide compatibility across various platforms and systems.


The mandatory start/stop characters, symbolized by asterisks, play a crucial role in the scanning process. These characters reduce the chance of misreads, ensuring that the encoded data is consistently interpreted correctly.

No Check Digit Required: 

While many barcodes necessitate a check digit for validation, Code 39 operates effectively without one. This streamlines the encoding process and reduces the chance of manual entry errors.

Integration Ease: 

Code 39's straightforward design and wide industry recognition make it easy to integrate into various software systems and databases. Whether businesses are revamping existing systems or implementing new ones, incorporating Code 39 often requires minimal effort.

what is a code 39 barcode

Design Rules of Code 39 Barcode

When creating or printing a Code 39 barcode, it's important to adhere to certain design rules to ensure its readability and functionality. Here are some of the key design rules:


The width ratio between narrow and wide elements (bars and spaces) must be consistent, usually between 2:1 and 3:1.

Quiet Zone: 

A quiet zone equal to the width of 10 narrow bars or spaces should precede the first character and follow the last character.


For Code 39 barcodes, it's advised to use printers with at least 203 DPI. However, smaller labels or the need for detailed prints may require over 300 DPI, as the clarity of the barcode impacts scanning accuracy and speed.


 While barcodes can be scanned in any orientation, a vertical (picket fence) orientation is the most common.


Barcodes should have a high contrast between bars (usually black) and spaces (usually white) for optimal scanning.

Applications of Code 39 Barcode

The versatility of Code 39 has led to its widespread adoption across various sectors. We will explore some of its uses below:


In manufacturing sectors, Code 39 aids in ensuring parts are easily traceable and identifiable, streamlining processes from assembly to quality control. Similarly, the automotive industry employs this symbology for parts tracking, ensuring the right components are used during vehicle assembly or repair. 

Example: A car manufacturer might label individual car parts with a Code 39 barcode. When a car is being assembled, workers can scan the barcode on each part to confirm its authenticity, verify that it's the correct part for the specific car model, and log the part's installation.


Many governmental agencies, including the U.S. Department of Defense, have chosen Code 39 for their standards due to its reliability and versatility. The LOGMARS system is based on Code 39 to reinforce the symbology's pivotal role in tracking and logistics within governmental operations. 

Example: During military exercises, equipment like tents, firearms, and radios might be labeled with Code 39 barcodes. When a unit checks out or returns equipment, the barcode is scanned to ensure accurate tracking and accountability of military assets.


In the world of healthcare, accuracy can literally be a matter of life and death. Code 39 is frequently employed for labeling lab specimens to ensure that each sample is correctly matched to a patient, and also for patient identification, mitigating the risk of medical errors. 

Example: When a patient provides a blood sample for testing, the vial is labeled with a Code 39 barcode that links to their medical record. This ensures that their test results are accurately reported back to the correct patient's file.


For libraries, efficiently managing thousands of books is crucial. Code 39 barcodes simplify the process of book check-in and check-out to ensure that each book's whereabouts are known and that patrons' borrowing histories are accurately maintained. 

Example: Each book in a library could have a Code 39 barcode label on its inside cover. When patrons borrow or return books, the barcode is scanned and it automatically updates the library's database with the book's current status and location.

Inventory and Asset Management: 

Businesses use Code 39 to manage their assets, from office equipment to specialized tools. This not only helps in preventing loss but also aids in maintenance scheduling and ensuring the right tools are available when needed. 

Example: A company might label its laptops with Code 39 barcodes. Employees can then check out laptops for business trips, and the IT department can track which laptops are currently in use, need maintenance, or are available for checkout.


While more commonly associated with non-retail applications, Code 39 can also be found in some retail environments, especially when items require multi-character identifiers. This can be especially useful for specialty retailers or businesses with unique inventory needs. 

Example: A specialty store selling rare vintage vinyl records might use Code 39 barcodes to label each record. This allows the store to easily manage its unique inventory, track sales, and reorder stock as necessary.

We hope our article has now left you with a better understanding of what Code 39 barcodes are and how they are utilized in different industries. 

If you enjoyed this article, you might also like our article on PDF417 barcodes or our article on Codabar barcode format.

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