Code 39 Barcode Scanner

What is a Code 39 barcode?

Code 39 is a one-dimensional (1D) barcode symbology standardized in ISO/IEC 16388. Developed in 1974, it was among the first barcodes to support alphanumeric data, including letters, numbers, and some special characters. Code 39 is also known as Code 3 of 9, Alpha39, Type 39, USD-3, and USS Code 39.

Each barcode includes start and stop characters (an asterisk) that help barcode scanners identify the code’s boundaries. Additionally, Code 39 includes an optional check character or check digit for enhanced error detection.

Code 39 barcodes are easily scanned by most barcode scanners and support manual verification thanks to their text interpretation below the barcode.

Code 39 vs Code 39 Extended (Full ASCII)

The standard Code 39 supports 43 characters (digits 0-9, uppercase letters A-Z, and seven special characters: -, ., $, /, +, %, and space). Code 39 Extended (also called Full ASCII Code 39) can encode the entire 128-character ASCII set.

Key characteristics of Code 39 Extended:

• Two-character combinations are used to represent characters beyond the basic 43. For example, “+E” is the combination for the lowercase letter “e”.
• Trade-off: Using these character pairs inevitably increases the barcode length.
• Less efficient for applications requiring extensive use of lowercase letters or special ASCII characters.

Structure and components

Code 39 relies on patterns of wide and narrow bars and spaces to encode characters. Each character is represented by 9 elements: 5 bars and 4 spaces. These include 3 wide and 6 narrow elements, corresponding to “3 of 9.”

The symbology can encode 43 characters: numeric digits (0-9), uppercase letters (A-Z), and seven special characters (-, ., $, /, +, %, and space).

Code 39 barcodes consist of the following key components:

1. Quiet zones: Blank areas on both sides of the barcode that ensure proper detection and readability.
2. Start character: An asterisk (*) that indicates the beginning of the barcode.
3. Data characters: The main content section where information is encoded.
4. Stop character: An asterisk (*) that indicates the end of the barcode.

Code 39 barcodes typically also show the following characteristics:

• X-dimension: The width of a narrow element (bar or space), typically 4-40 mils
• Inter-character gap: Space between individual encoded characters, usually equal to one narrow bar width
• Bar ratio: Relation between narrow and wide elements, often 1:2 to 1:3, with 1:2.5 recommended
• Self-checking property: Design largely prevents single-character errors from generating valid misreads, enhancing reliability

Encoding and error detection

Each character pattern is assigned a numeric value, as shown in the table below.

These values are used to calculate the checksum. This is an optional modulo 10 or 43 check character added to the end of the Code 39 barcode for error detection.

Here’s how the checksum is calculated and encoded:

1. Assign numeric values to each character in the data portion of the barcode (using the table).
2. Sum all those numeric values together.
3. Divide the sum by 43 (the number of possible values) or 10.
4. The remainder of that division is the checksum value.
5. The character corresponding to this value is appended to the barcode.

In step 3, the sum of all character values is divided either by 43 (MOD43) or 10 (MOD10).

Using Modulo 43 (MOD43), taking the remainder of dividing by 43 as the code checksum, is most common. Since Code 39 encodes 43 characters, this ensures the remainder always maps to a valid character. This provides stronger error detection on alphanumeric data.

Modulo 10 (MOD10) produces only numeric check digits between 0 and 9. This is sufficient for numeric-only cases but is otherwise less robust in the case of alphanumerical codes.

For example, some inventory or batch control systems use Code 39 but restrict data to numbers. This is common for carton IDs or shipment batches. In these cases, a simple Modulo 10 checksum is enough to catch common input or scanning errors. The calculation is lightweight because the digits are summed as-is, without need for the lookup table, since digits count as themselves in the checksum calculation.

Industry Standards and Compliance

Code 39 has been adopted by numerous industry organizations and standardized for specific applications. This ensures interoperability and compliance across sectors.

Let’s take a brief look at some of the most important standards:

LOGMARS (Logistics Applications of Automated Marking and Reading Symbols):

• Official standard used by the US Department of Defense (DoD)
• Defined by Military Standard MIL-STD-1189B and related specifications
• Mandates specific placement, size, and data encoding requirements for military supply chain items
• Requires Modulo 43 checksum for enhanced data integrity.

HIBCC (Health Industry Business Communications Council):

• Healthcare industry labeling standard, focused on patient safety
• Applied to patient wristbands, medication packaging, and surgical instruments
• Used for unique device identification (UDI) on medical equipment
• Supports both Code 39 and Code 128 implementations, as well as 2D barcodes.

AIAG (Automotive Industry Action Group):

• Standard for labeling in the automotive manufacturing sector
• Specifically adopted for VIN (Vehicle Identification Number) barcode encoding
• Enables continuous part tracking throughout automotive supply chains
• Facilitates automated assembly line processes and quality control.

Code 32 (Italian Pharmacode)

Code 32, also called Italian Pharmacode or Codice Farmaceutico, is a specialized variant of Code 39, designed specifically for pharmaceutical product identification in Italy. It encodes the AIC (Autorizzazione all’Immissione in Commercio) identifier.

Key characteristics of the Italian Pharmacode:

• Mandated by Italian pharmaceutical regulations for medicine identification and traceability
• Derived from Code 39 symbols, but with a more limited character set of 32 characters: the digits 0-9 and the English alphabet excluding the letters A, E, I, O
• The code consists of nine digits, the first of which is zero and the last a check digit
• The checksum is calculated using MOD10
• Ensures compatibility with pharmacy IT systems and supports anti-counterfeiting measures.

Applications of Code 39 barcodes

Manufacturing and automotive

Code 39 is common in the automotive industry and factory automation for tracking components, products, and work-in-progress items. It was also adopted by the Automotive Industry Action Group as the standard VIN Barcode.

Healthcare

In the healthcare sector, Code 39 barcodes are used for patient identification, medication management, and equipment tracking. In particular, the Health Industry Bar Code Council (HIBCC) regulates their use on wristbands, medication packaging, and medical devices.

Logistics

Code 39 barcodes are widespread in logistics applications, including inventory management, warehouse operations, and shipping processes.

Military and government

The United States Department of Defense uses Code 39 under the LOGMARS (Logistics Applications of Automated Marking and Reading Symbols) standard to label supplies and equipment.

Code 39 Comparison Table with other popular Barcode types

Feature	Code 39	Code 128	UPC (UPC-A)	Code 93
Character Set	43 chars (0–9, A–Z, 7 symbols)	Full ASCII (128 chars)	Numeric only	43 characters + full ASCII (128 chars)
Data Density	Low	High	Medium	Medium–high
Length Limit	No theoretical limit	No theoretical limit	Fixed (12 digits)	No theoretical limit
Checksum	Optional (MOD43 / MOD10)	Mandatory (MOD103)	Mandatory	Mandatory, 2× MOD47
HRI	Yes	Yes	Yes	Yes
Typical Use Cases	Industrial, military, healthcare	Retail, shipping, logistics	Retail products	Postal and logistics
Year Introduced	1974	1981	1973	1982
Print Tolerance	High	Medium	Medium	Medium
Scanner Support	Universal – typically enabled by default	Universal – typically enabled by default	Universal – default on POS scanners	Universal – enable “Code 93”

 

Code 39 Variants at a Glance Code 39

 

Feature	Code 39 Standard	Code 39 Extended (Full ASCII)	Code 32 (Italian Pharmacode)
Character Set	43 chars (0–9, A–Z, 7 symbols)	Full ASCII (128 chars via 2-character combos)	43 chars (0–9, A–Z, 7 symbols)
Data Density	Low	Lower (longer barcodes due to 2-char encoding)	Compact (fixed length)
Checksum	Optional (MOD43 / MOD10)	Optional (MOD43 / MOD10)	Mandatory check digit (MOD10)
Typical Use Cases	Industrial, military, healthcare	Applications requiring lowercase/special characters (full ASCII)	Italian pharmaceutical packaging
Scanner Support	Universal – typically enabled by default	Universal – enable “Code 39 Full ASCII”	Universal – enable “Code 32 / Italian Pharmacode”

 

Why choose the Scanbot SDK for Code 39 scanning?

 

The Scanbot Barcode Scanner SDK is specifically designed to handle the challenges of decoding Code 39 barcodes in real-world scenarios. What sets us apart:

 

• Exceptional performance: Reliably decodes even damaged, low-contrast or distorted barcodes.
• High-speed scanning: Read Code 39 barcodes in as little as 0.04 seconds.
• Cross-platform compatibility: Easily integrate with Android, iOS, cross-platform, web, Windows, and Linux platforms.
• Customizable UI: Customize the ready-to-use components to match your app or website design.
• Privacy-first: Operates offline for complete data security.

 

Our SDK supports both standard and Extended Code 39 formats. Once Extended Code 39 is enabled in the configuration, the SDK automatically detects whether a barcode uses standard or extended encoding and decodes the content accordingly.

 

It also supports proper Human Readable Interpretation (HRI) formatting when displaying the result. HRI refers to the text shown below the barcode.

 

For Code 39, specifically, the scanner can output the encoded information with or without the start/stop asterisks or checksum characters. Our SDK conforms to industry standards and regulations (such as LOGMARS for defense or HIBCC for healthcare) to ensure the HRI is displayed consistently and in the required format.

 

Whether your use case involves Code 39 barcodes, QR codes, or any other barcode, the Scanbot SDK delivers the accuracy, speed, and reliability you need to succeed.

 

How to build a Code 39 Barcode Scanner in JavaScript

 

Creating a browser-based Code 39 Barcode Scanner is straightforward. In the following example, we’ll implement it in a single stand-alone HTML file.

 

 

To achieve this, we’ll use plain JavaScript and the Scanbot Web Barcode Scanner SDK.

 

First, create an index.html with some boilerplate code.

 

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta
            name="viewport"
            content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0"
        />
        <title>Code 39 Barcode Scanner</title>
    </head>
    <body>    
    </body>
</html>

 

To set up our scanner, we’ll have to do the following:

 

• Create a button that calls up the scanning interface when clicked.
• Include a <p> element on the page for displaying the scanning result.
• Import the Scanbot Web SDK using a CDN.
• Process the scan result before displaying it on the page.

 

⚠️ In this example, we’re importing the SDK via jsDelivr. However, you should only do this for quick prototyping. In your production environment, please download the Web SDK directly (or install it via npm) and include its files in your project.

 

The result should look something like this:

 

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta
            name="viewport"
            content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0"
        />
        <title>Code 39 Barcode Scanner</title>
    </head>

    <body style="margin: 0">
        <button id="start-scanning">Start scanning</button>
        <p id="result"></p>
        <script type="module">
            import "https://cdn.jsdelivr.net/npm/scanbot-web-sdk@7.0.0/bundle/ScanbotSDK.ui2.min.js";
            const sdk = await ScanbotSDK.initialize({
                enginePath:
                    "https://cdn.jsdelivr.net/npm/scanbot-web-sdk@7.0.0/bundle/bin/barcode-scanner/",
            });
            document
                .getElementById("start-scanning")
                .addEventListener("click", async () => {

                    const config =
                        new ScanbotSDK.UI.Config.BarcodeScannerScreenConfiguration();

                    const scanResult = await ScanbotSDK.UI.createBarcodeScanner(config);
                    if (scanResult?.items?.length > 0) {
                        document.getElementById("result").innerText = scanResult.items[0].barcode.text;
                    } else {
                        document.getElementById("result").innerText = "Scanning aborted by the user";
                    }
                });
        </script>
    </body>
</html>

 

💡 We use Web Barcode Scanner SDK version 7.0.0 in this tutorial. You can find the latest version in the changelog.

 

This already provides us with a fully functional barcode scanner that will read any barcode type. Restricting it to scanning only Code 39 prevents unintended scans and improves the scanner’s performance, as it doesn’t need to check each supported symbology.

 

So let’s restrict scanning to the Code 39 symbology by modifying the BarcodeScannerScreenConfiguration we assigned to the config constant in the previous step.

 

config.scannerConfiguration.barcodeFormats = ["CODE_39"];

 

You can also change the viewfinder’s aspect ratio. It’s square by default, but since Code 39 comes in a horizontal format, it makes sense to also convey this in the scanning interface. This is mainly a cosmetic change, but do keep in mind that only barcodes located inside the viewfinder will be scanned.

 

config.viewFinder.aspectRatio.height = 1;
config.viewFinder.aspectRatio.width = 2;

 

Your final index.html will look like this:

 

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta
            name="viewport"
            content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0"
        />
        <title>Code 39 Barcode Scanner</title>
    </head>

    <body style="margin: 0">
        <button id="start-scanning">Start scanning</button>
        <p id="result"></p>
        <script type="module">
            import "https://cdn.jsdelivr.net/npm/scanbot-web-sdk@7.0.0/bundle/ScanbotSDK.ui2.min.js";
            const sdk = await ScanbotSDK.initialize({
                enginePath:
                    "https://cdn.jsdelivr.net/npm/scanbot-web-sdk@7.0.0/bundle/bin/barcode-scanner/",
            });
            document
                .getElementById("start-scanning")
                .addEventListener("click", async () => {

                    const config =
                        new ScanbotSDK.UI.Config.BarcodeScannerScreenConfiguration();
                    config.scannerConfiguration.barcodeFormats = ["CODE_39"];

                    const scanResult = await ScanbotSDK.UI.createBarcodeScanner(config);
                    if (scanResult?.items?.length > 0) {
                        document.getElementById("result").innerText = scanResult.items[0].barcode.text;
                    } else {
                        document.getElementById("result").innerText = "Scanning aborted by the user";
                    }
                });
        </script>
    </body>
</html>

 

Now run the app and scan a Code 39 to test your scanner!

 

 

💡 You can run the Scanbot SDK for 60 seconds per session without a license. For more in-depth testing, we recommend you generate a free trial license.

 

For more information on how to customize your scanner, head over to the documentation.

 

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