The symbology that you use is determined by several factors: 

• The amount, size, and type of data to be encoded
  The type of data that you generate will help determine what symbology to use. All barcode symbologies can encode numbers, and many can also encode letters and special characters (such as the full ASCII character set). Numeric-only symbologies include UPC/EAN and ITF-14. Alphanumeric symbologies include Code 128, Code 39 - Regular, QR Code, and Data Matrix.

• Industry standard requirements
  In some cases, the symbology is predetermined by an industry application standard. For example, retail products must be marked with UPC/EAN.

• Size constraints
  Very small products or labels can accommodate only those symbologies that can be marked in a small space, such as Data Matrix. Additionally, the resolution of the printer that is used to print the symbol is a factor, as printer resolution affects the available X dimension measurements and therefore the symbol size (higher resolution printers can print smaller symbols).

• Security and error-checking requirements
  Some symbologies are or can be made more secure than others, and not all use check digits for error correction.

• Printing environment
  Will the symbol be printed on corrugated cardboard? Will direct parts marking methods be used? Will the symbols be printed in-house or by a printer service, or will they be emailed? What are the resolution requirements? (Some symbols are more forgiving of imprecise printing than others.)

• Scanning environment
  Will the symbols be scanned at a point of sale by a person or in a warehouse by machines? Is the scanning surface curved (as with barrels)? How likely are the symbols to be damaged by the environment? (Some symbols can be read even when damaged.)

• Price
  Some symbols are proprietary and require licensing. Others are in the public domain.

Create or obtain the data that you need to encode, such as stock keeping units (SKUs), part numbers, lot numbers, expiration dates, location numbers, URLs, and so on. (Depending on the barcode generation software that you use, this data can be stored in a database, a Microsoft Word document, or a Microsoft Excel spreadsheet.) If you are using the GS1 system, you will be assigned a company prefix, and you will create your own Global Trade Item Number (GTIN) and other GS1 identification keys as needed, all of which must be encoded as well.

Commercially-available software can make it easy to create barcode symbols. Physical elements to be considered include the following:

• Size
  The size of the barcode that you create depends on where it will be placed and how it will be printed. For example, most codes require a quiet zone (blank space) around the symbol, which uses more space than the symbol alone uses. Also, to prevent scanning errors, linear codes should not be truncated to fit on a package. Industry standards sometimes define the dimensions that are required for the symbol to be in compliance.

• Color
  The optimal color combination for a barcode symbol is black bars or squares with white spaces and quiet zones. A few other colors can be used but are not generally recommended.

• Placement
  The placement of the barcode on the package can affect the ability of scanners to read it. For example, the edge of the package or product should be avoided to allow enough space for a quiet zone.

To verify that the barcode that you created scans correctly and reliably, you can do one of the following:

• Use a verification service (either through GS1 or a third-party provider).

• Purchase and use your own verification equipment.

For more information, see the AIM Layman's Guide to ANSI, CEN, and ISO/IEC Linear Bar Code Print Quality Documents publication.