ISO/IEC 15416 Barcode Print Quality Test Specifications for Linear Symbols and ISO/IEC 15415 Barcode Print Quality Test Specifications for 2D Symbols describes methods for assessing the quality of barcode symbols after they are printed. An ISO-based verifier looks at the symbol in the way a scanner does but goes further by grading the symbol's quality.
GS1 barcode standards utilise the ISO/IEC methods, specifying the minimum grade necessary for every standardised GS1 barcode based on which symbol is used, where it is used, or what identification number it is carrying. In addition to the minimum grade, GS1 also specifies the verifier aperture width and wavelength.
Setting up different minimum specifications is similar to a university using a standardised test to determine whether applicants qualify for admission. Several universities may utilise the same standardised test, but each sets the minimum score necessary for its applicants to be admitted.