GS1 Application Identifier lookup & parser.

How GS1 element strings work

A GS1 barcode such as GS1-128 or GS1 DataMatrix carries data as a string of elements. Each element is an Application Identifier (a 2 to 4 digit prefix that says what the data is) followed by its value. Some AIs have a fixed length, such as 01 (GTIN, 14 digits), 00 (SSCC, 18 digits), 11 and 17 (dates, 6 digits, YYMMDD) and 310n (net weight in kg, 6 digits, where the last AI digit is the number of decimal places). Those need nothing after them. AIs with variable length, such as 10 (batch/lot) and 21 (serial), must be ended by an FNC1 separator (ASCII group separator, 0x1D) unless they are the last element.

What is verified

• The AI is in the GS1 list this tool carries (AIs 00 to 99 and 200 to 499, the 31nn to 36nn measure families and 39nn amounts).
• Value length and character type: N is digits only, X is GS1 character set 82.
• The GS1 mod-10 check digit on GTIN (01, 02, 03), SSCC (00), GLN (410 to 417, 253, 255) and GSIN (402).
• Dates: month 01 to 12 and a day valid for that month (day 00 is allowed by GS1). The century is not decided because it depends on the current date.

What is not verified

This checks format and check digits only. It cannot confirm that a GTIN, SSCC or GLN was ever issued by GS1. Content rules that need lookup tables (country and currency codes, GS1 Company Prefix length, percent-encoded text) are not applied, and AIs outside the list above are shown as “not in this list” rather than invalid. If a raw string has no separators, a variable-length AI reads on until its maximum length, so use the bracketed form or insert separators where the string is ambiguous.

The same check digit engine is available on its own in the GLN / SSCC / GTIN validator.

Sources: GS1 Barcode Syntax Dictionary, github.com/gs1/gs1-syntax-dictionary (maintained by GS1 AISBL); GS1 AI register, ref.gs1.org/ai, via python-stdnum stdnum/gs1_ai.dat; GS1 General Specifications, Release 26.0, section 3, gs1.org.