How to choose the Right Barcode Type for Your Application: the TL;DR guide

This is a quick guide for new applications. It's basic, so we'll only cover the most obvious few choices: UPC-A, EAN 13, Code 128, Code 39, QR Code, Datamatrix. Those are the major codes in use today.

There are others, but you aren't missing much. OnMerge supports many other codes, but they're mainly used in specific industries, or they're legacy codes used for compatibility with older applications.

Likewise, we'll only go over the major factors that might go into your decision. If you already have a system in place or have been given specifications, it's best to stick with what you've been given unless there's a good reason to switch.

Do you need to meet a third party's requirements? The choice is obvious if, say a trading partner, specifies you must use a certain barcode such as UPC-A, Amazon FNSKU, ITF-14, SSCC-18, GS1-128 and others.

Do you already have scanners you must support? Check what barcodes they support. Most modern scanners support all the major linear (1D) and 2D barcodes, but older or inexpensive models may only support a few linear types such as Code 39. Older scanners are less likely than newer ones to support 2D codes like QR Code and Datamatrix.

Will barcodes be scanned with smartphones? Sometimes? Smartphone scanners vary, but many phones can read UPC-A, EAN 13, Code 128, Code 39, QR Code and Datamatrix. UPC-A, EAN 13 and QR Code are the surest bets. However, phones are mediocre scanners because their cameras' resolution is limited, so you it's best to keep the codes short. If you have more than 10 - 15 characters to encode, use QR Code or Datamatrix to avoid a wide, thin linear barcode that's hard to fit into a phone's scanning window.

iPhones? Apple iPhones™ have a built-in scanner for QR codes only—swipe up from the very bottom of the screen to access. Scanning other types of barcodes requires third-party apps, though there are many free ones available.

Will you be printing the barcodes under well-controlled conditions, or will they be printed on a wide variety of printers, or by users or others?
Will barcodes be e-mailed, or possibly photocopied? Linear barcodes such as UPC-A, EAN 13, Code 128 require precise printing to scan correctly because they rely on very precise relationships between the widths of the black vs white bars. Code 39 is somewhat more resilient to distortions caused by varying print conditions or copying, but the most resilient codes are are the 2D ones: QR Code and Datamatrix.

Are barcodes subject to being damaged, for example by rips, weather, smudges, scrapes, stains (e.g. coffee), holes, staples, getting written on, etc? If so, QR Code or Datamatrix are your natural choice since they have built-in correction that can recover from many kinds of damage.

What's the nature of your data? If you are coding UPC or EAN product identfiers, the familiar UPC-A (in North America) or EAN (rest of the world) codes are the way to go. Many POS scanners work only with UPC or EAN barcodes. Otherwise, stick to Code 128, Code 39, QR Code or Datamatrix.

Most consumers easily recognize QR Codes, so they're the obvious choice for website links (URLs), vCards, phone numbers, or other consumer-oriented applications where you want to say "scan me."

Up to how much data will be encoded in the barcode? UPC and EAN must contain exactly 11 and 12 digits (numbers) respectively, plus one check digit which is auto-generated. That last check digit is beyond your control. Code 39 barcodes are very space-inefficient, so barcodes become overly wide over 6 - 8 characters.

Width is an issue because it's tricky to accurately hold a scanner steady over a very wide and skinny barcode. That can slow the scanning process. Code 128 is more space-efficient, and barcodes up to 15 - 20 characters can be efficiently scanned. For more data than that, seriously consider using QR Code or Datamatrix.

Are undetected scan errors a big deal in your application? All barcodes have some degree of error-checking built in, but UPC, EAN and Code 39's error detection is far from foolproof, with scans that appear successful but yield inexact data. Code 128 has much improved error-checking built in, but it isn't absolutely foolproof. QR Code and Datamatrix have industrial-strength error-detection built in. They can detect over 99.99999% of scanning errors, and can automatically correct most of those.

Code 39	Code 39 is known for being fast and easy to scan using even the oldest and cheapest scanners. Again, fast and easy. They carry a very limited amount of information (6 - 8 characters in the real world), take up considerable space, and can be subject to undetected scanning errors. Can be sensitive to varying printing conditions or photocopying. Use this where printing is under the organizers' control, and fast and easy scanning of large numbers of short codes trumps other considerations. One popular application is conference badges.
Code 128	The most sophisticated of the linear barcodes, defined by official international standards. Can carry a moderate amount of information (15 characters scan easily, up to 32 in some circumstances). Have fairly reliable error-checking built in. More sensitive to variations in printing than Code 39. Does not photocopy well. Scanning may be slow. You may notice a choice between A, B, C and Automatic "encoding." That choice is mainly for people who have to comply with an existing, external requirement. If you have the choice, just choose Automatic and let the barcode encoder choose the best encoding for the particular data.
UPC-A EAN 13	Use these codes only for product identifiers (UPC in North America, EAN elsewhere) that will be scanned at checkout counters. There are better alternatives for other data. They require crisp, black, high-quality printing, which means they must be printed under your control. Most smartphones can read them, but some models (earlier iPhones, for example) can take a long time to scan them.
Datamatrix	These barcodes are industrial workhorses that can carry a lot of data reliably. Although not as well-known as QR Codes, they're used extensively, for example, on electronic postage stamps. Datamatrix is known as a bullet-proof barcode, and is sometimes demonstrated by successfully scanning barcodes that have been used for target practice! Datamatrix codes are fairly insensitive to printing variations because scanners are insensitive to the exact size of the dots that make up the code, and because they have lots of error-correction built in. This makes Datamatrix codes ideal for printing by users or display on smartphones. Most scanners (and smartphones) can read these just as easily as QR Codes, though iPhone's default built-in scanner can't. They will typically bring up URL web links in the same way as QR, but consumers aren't as familiar with them. This can be an advantage if you don't want a barcode that encourages curious users to scan it and ask questions about its contents. All in all, Datamatrix is considered a slightly more robust code than QR Code.
QR Code	These barcodes scream "scan me!" Though Datamatrix will do the same job just fine, but consumers have been trained to recognize QR Codes for web links (URLs), vCards, and so forth, so these are best for marketing purposes. QR Codes are fairly insensitive to printing variations because scanners are insensitive to the exact size of the dots that make up the code, and because they have lots of error-correction built in. This makes QR codes ideal for printing by users or display on smartphones. When encoding URLs, it's best to use a URL shortener. While QR codes can carry large amounts of data, more data means that the pattern of dots becomes more intricate. The more intricate pattern is more difficult to read for low-quality scanners like smartphones, and low-quality printing becomes more of an issue. vCards and MeCards contain quite a bit of data and can be significantly less likely to scan successfully than, say, a shortened URL. QR Codes have extremely robust error-checking and recovery which enable scanning even if a significant portion of the code is damaged, but some scanners (and most smartphones) often miss the opportunity to correct a damaged QR Code because they can't even "see" a QR Code when any of the three square "eyes" in the corners of the code are damaged.