You can identify a barcode symbol type just by looking at it. It is a handy skill to have when a scanner or verifier is not readily available. You do not need to understand how the barcode is structured or how the decode algorithm works. Barcode symbol type, AKA “symbology”, is visually identifiable by the pattern of bars and spaces at the start and stop of the barcode.
UPC/EAN
This symbology is the simplest to identify visually. All begin with a pair of narrow bars with a narrow space between them. The full 13-digit version also has an identical pair at the end.
The shortened EAN-8 and UPC-E versions also have this telltale pattern of start and stop bars.
ITF-14
This barcode also has an easily identifiable set of start/stop bars, with a pair of narrow bars with an equally narrow space between them at the start, and at the stop, a wide and narrow bar with a narrow space between them.
ITF-14 should also have a long dark horizontal bar above and below the bar/space pattern, and in many usages has a full-surrounding bearer bar frame.
ITF-14 is a GS1 barcode type. Non-GS1 versions of ITF barcodes are in use in closed-loop systems, and may not have the same identifiable bar/space pattern characteristics.
Code 39 is identifiable by a start pattern of narrow and wide bars as follows: NNWWN (N = narrow, W = wide)
If you look closely, you will see the same pattern at the end of a Code 39 barcode.
GS1-128 is a bit more complicated. Code 128 has three possible character sets, each of which encode data differently. But all three character sets share a common stop character pattern: two wide bars flanking a narrow bar-space-bar pattern.
(See GS1 General Specification Release 21.0.1 page 298.)
GS1-128 is a GS1 barcode type. Non-GS1 versions of Code 128 are in use in closed-loop systems, and may not have the same identifiable bar/space characteristics.
DataBar is readily identifiable in its stacked configuration. DataBar also makes common use of a single narrow start and stop bar.
Datamatrix Code always has an L track consisting of a solid dark line of two adjacent sides, and a clock track of alternating light-dark elements on the opposite adjacent sides.
QR Code utilizes a finder pattern consisting of a dark square within a dark frame in three corners. A similar, smaller alignment pattern is often located inboard of the fourth corner.
Scanning systems security often involves limiting the types of barcodes it will accept. When a barcode fails to scan, it can be difficult to determine the cause. Visual identification of a barcode type can simplify this.
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