Barcode Generator

About the Barcode Generator

A linear barcode is a row of bars and spaces of different widths that a scanner reads as a series of characters. Different industries settled on different encodings, called symbologies, and each has its own rules about which characters it can hold and how its error checking works. This generator draws five of the most widely used ones: CODE128 for general text and numbers, CODE39 for simple uppercase labels, EAN-13 and UPC-A for retail product numbers, and ITF-14 for shipping cartons. You type the content, pick the type, and the barcode appears immediately with the human-readable text underneath.

What you type has to suit the format, and the tool tells you when it does not. EAN-13 wants 12 or 13 digits, UPC-A wants 11 or 12, and ITF-14 wants 13 or 14. In the retail formats the last digit is a check digit, a number calculated from the others that lets scanners catch misreads. If you supply one fewer digit than the full length, the generator calculates and appends the check digit for you. If you supply the full length, it verifies the final digit and refuses to draw a code that does not match.

The image is drawn in a browser canvas with the narrowest bars two pixels wide, bars 90 pixels tall, a 12 pixel margin, and dark ink on white, and you can save it as a PNG with one click. That makes it practical for inventory labels, asset tags, event passes, library shelves, and test data for software that reads barcodes. One caution matters for products: a code that scans is not the same as a code you are entitled to use for goods sold in stores, since retail numbers are issued through the GS1 system.

When to Use It

How to Use It, Step by Step

1. Click the 'Barcode type' dropdown first and choose the symbology. CODE128 is the most flexible, CODE39 suits uppercase labels, EAN-13 and UPC-A are retail product formats, and ITF-14 is the shipping carton format.
2. Read the short hint line under the two fields. It tells you what the chosen type accepts, for example 'Exactly 12 or 13 digits' for EAN-13, and it changes each time you switch the type.
3. Click the 'Content to encode' box and type or paste your text or number. The field starts with EVERYFIX-123 as a sample, so replace it with your own value.
4. Watch the barcode redraw as you type. The human-readable characters appear beneath the bars, and for EAN and UPC codes the digits are split around the guard bars the way they are on retail packaging.
5. If the content does not fit the chosen type, the barcode disappears and an amber message says it 'doesn't fit the selected barcode type' with the rule repeated. Fix the entry or switch to CODE128.
6. Check the check digit when you enter a full-length retail code. If the last digit is wrong, the tool treats the barcode as invalid instead of silently changing it. To have it calculated for you, omit the last digit.
7. When the barcode shows, press 'Download PNG' to save it. The file is named after the type, for example barcode-code128.png, barcode-ean13.png, barcode-upc.png, barcode-itf14.png, or barcode-code39.png.
8. Print a test copy at the size you intend to use and scan it with the actual reader before printing a batch. Leave blank space on both sides of the bars so the scanner can find the start and stop patterns.

Understanding Your Results

The result is the barcode image itself, plus the readable text under the bars. The width of the image depends on the content and the format: a longer value needs more bars. In CODE128, the 12-character default EVERYFIX-123 takes 167 narrow-bar units, while the eight digits 12345678 take only 79, because CODE128 can pack two digits into one character when it sees a run of numbers. At the tool's two pixel bar width, that is about 334 versus 158 pixels of bars, before the margins.

For EAN-13 and UPC-A, the printed digits include the check digit, so the number under the bars may be one longer than what you typed. For example, entering the 11-digit UPC body 03600029145 results in the 12-digit code 036000291452. ITF-14 and the other formats follow similar logic. Compare the printed number against your source to confirm you got what you expected, particularly when you relied on the tool to add a final digit.

If no barcode appears, the content does not satisfy the format rules. The most common reasons are the wrong number of digits for EAN, UPC, or ITF-14, a wrong check digit, letters or symbols in a numeric format, or characters outside the plain ASCII range in CODE128, such as accented letters. CODE39 accepts only digits, capital letters, and the symbols hyphen, period, space, dollar, slash, plus, and percent. Switch formats if your content needs more freedom.

More Worked Examples

Tips for Better Results

• Use CODE128 whenever you are making your own internal labels. It handles upper and lower case letters, digits, and common punctuation, and it is supported by nearly every scanner, so you rarely need a more restrictive format.
• Keep identifiers short. Every extra character widens the barcode, and a very wide code printed on a small label forces the bars to shrink, which makes scanning slower and less reliable.
• Print at actual size without scaling to fit the page. Retail EAN and UPC symbols are commonly specified with a nominal bar width of about 0.33 millimeters, and shrinking an image far below its natural size can blur the narrowest bars.
• Keep high contrast and a clean background. Dark bars on plain white or light paper scan best, while glossy lamination, colored paper, or patterns behind the bars can cause misreads.
• Leave quiet space on both sides. Scanners need a clear margin to find where the code begins and ends, so do not crop the PNG tightly or place the code against a border or another graphic.
• Test with the actual device that will read the codes. A phone camera, a laser scanner, and a warehouse handheld each behave differently, and a quick scan of a printed proof avoids discovering problems after hundreds of labels.

Common Mistakes to Avoid

• Using a made-up EAN or UPC number for a product to be sold in stores. Valid-looking digits are not registered to your company, and retailers and online marketplaces generally require numbers licensed through GS1.
• Typing a full-length retail code with a guessed last digit. The tool checks it against the calculated check digit and marks it invalid when they differ, so omit the final digit and let the generator add it.
• Choosing CODE39 and entering lowercase or special symbols. It converts letters to uppercase but rejects characters outside its small set, so pick CODE128 when you need freedom.
• Saving the image and resizing it by stretching. Changing only the width or height distorts the bar proportions, so scale the whole image evenly, or regenerate it.
• Forgetting what the barcode contains. A code is only a pattern for the characters you typed, so record which identifier belongs to which item, or you will end up with perfectly readable labels that nobody can interpret.

Assumptions and Limits

• The generator encodes exactly the characters you supply, apart from adding a check digit to EAN-13, UPC-A, and ITF-14 when one is missing. It does not look up products, register numbers, or confirm that a number belongs to anyone.
• Appearance is fixed: narrowest bars two pixels wide, bars 90 pixels tall, a 12 pixel margin, 16 pixel text, and near-black ink on white. The PNG is a raster image at that size, so extreme enlargement will soften the edges.
• CODE128 is limited here to plain ASCII text, CODE39 does not include an optional check character, and ITF-14 is drawn without any extra carton frame or packaging markings. Industry labeling standards can add requirements this tool does not handle.
• A barcode that looks right on screen may still scan poorly if printed badly. For regulated, retail, or shipping uses, confirm the specification with your customer, carrier, or the GS1 organization in your country.

Key Terms

Symbology

A specific system for encoding characters as bars and spaces, such as CODE128 or EAN-13. Each symbology defines which characters it supports and how it checks for errors.

Check digit

A final number calculated from the other digits, used by a scanner to verify that the code was read correctly. A mismatch signals a misread or a typing error.

EAN-13

A 13-digit retail barcode used across much of the world, including the final check digit. It is the international counterpart of the North American UPC-A.

UPC-A

A 12-digit retail barcode used mainly in the United States and Canada. Eleven digits identify the product and the twelfth is a check digit.

GS1

The standards organization that administers company prefixes and product numbers for retail barcodes. Businesses that sell through major retailers typically license their numbers from it.

Quiet zone

The blank margin to the left and right of a barcode that lets a scanner detect where the pattern starts and stops. Cropping it too tightly causes scan failures.