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Application Identifiers

GS1 Application Identifiers (AIs) are standardized numeric prefixes that define the meaning of the data that follows them. In a GS1 Digital Link URI, AIs appear as path segments, encoding product identification data directly in the URL structure.

In a traditional barcode, AIs are encoded as numeric prefixes within the data stream. In a Digital Link URI, they become URL path segments in pairs of /{AI}/{value}:

https://gtin1.com/01/00785034739064/10/LOT2024A/17/261231
                   ── ──────────────── ── ──────── ── ──────
                   AI  GTIN value       AI  Lot     AI  Expiry

The first AI in the path is always the primary key -- the GS1 identifier that uniquely identifies the item or entity. Subsequent AIs are qualifiers that add context about a specific instance.

Primary Key AIs

Primary key AIs identify the type of GS1 key being resolved. See Digital Link Resolution for the full list of supported primary keys.

The GTIN (AI 01) is the most common primary key. It identifies a trade item (product) and is the only primary key with full resolution support in GTIN1 today.

Qualifier AIs for GTIN Resolution

When a GTIN Digital Link URI contains additional path segments, GTIN1 parses and validates each qualifier AI. These qualifiers narrow the scope from "this product" to "this specific batch, serial number, or date" of the product.

Identification and Serialization

AI Title Description Format Example
10 Batch/Lot Batch or lot number Up to 20 alphanumeric characters /10/LOT2024A
21 Serial Serial number Up to 20 alphanumeric characters /21/SN00001

These are the most commonly used qualifier AIs. Together with the GTIN, they uniquely identify a specific unit of a product.

Date Tracking

AI Title Description Format Example
11 Production Date Date the product was manufactured YYMMDD /11/240115
13 Pack Date Date the product was packaged YYMMDD /13/240120
15 Best Before Best before or best by date YYMMDD /15/250630
16 Sell By Sell by date YYMMDD /16/250615
17 Expiration Use by or expiration date YYMMDD /17/251231

All dates use the six-digit YYMMDD format. For example, December 31, 2025 is encoded as 251231.

Tip

Date AIs in the URI path are passed through to the product page as query parameters, enabling context-aware display of expiration and freshness information.

Product Variants

AI Title Description Format Example
20 Internal Variant Internal product variant number 2 digits /20/01
22 Consumer Product Variant Consumer-facing variant Up to 20 alphanumeric characters /22/REDLARGE

Additional Identification

AI Title Description Format Example
235 TPX Third-party controlled serialized extension of GTIN Up to 28 alphanumeric characters /235/EXT12345
240 Additional Product ID Manufacturer-assigned additional product identifier Up to 30 alphanumeric characters /240/MFGPART99
241 Customer Part Number Part number assigned by the customer Up to 30 alphanumeric characters /241/CUSTPART01
242 MTO Variant Made-to-order variation number Up to 6 digits /242/001234
243 Packaging Component Packaging component number Up to 20 alphanumeric characters /243/PKG01

Traceability (FSMA 204)

AI Title Description Format Example
416 Production/Service Location GLN of the production or service location 13 digits /416/4012345000015
7007 Harvest Date Harvest date or date range YYMMDD or YYMMDDYYMMDD /7007/240901

These AIs support FDA FSMA Rule 204 (Food Traceability) requirements, which mandate tracking of certain foods through the supply chain. Products on the Food Traceability List (FTL) benefit from including these AIs in their Digital Link URIs.

Validation Rules

GTIN1 validates each AI value against its defined format:

  • Date AIs (11, 13, 15, 16, 17): Must be exactly 6 digits in YYMMDD format with valid month (01-12) and day (00-31) ranges. Day 00 means "unspecified day" per the GS1 General Specifications.
  • Batch/Lot (10) and Serial (21): Up to 20 characters from the GS1 alphanumeric character set.
  • Internal Variant (20): Exactly 2 digits.
  • MTO Variant (242): 1 to 6 digits.
  • Production Location GLN (416): Exactly 13 digits.
  • Harvest Date (7007): 6 digits for a single date, or 12 digits for a date range.

If an AI in the path has an invalid value, the resolver returns a 400 Bad Request error with a descriptive message. If the path contains a segment that is a valid AI format (2-4 digits) but is not a recognized AI code, the resolver allows it through without error.

URI Construction Examples

Here are examples of how to construct Digital Link URIs with different combinations of AIs:

https://gtin1.com/01/00785034739064

Resolves to the product information page for this GTIN.

https://gtin1.com/01/00785034739064/10/LOT2024A

Resolves with lot context, enabling batch-specific information display.

https://gtin1.com/01/00785034739064/10/LOT2024A/21/SN00001

Identifies a specific unit. The resolver can display serial-level traceability data.

https://gtin1.com/01/00785034739064/17/261231/10/BATCH99

Includes expiration date and batch number. The product page can show remaining shelf life.

https://gtin1.com/01/00785034739064/10/LOT2024A/416/4012345000015/7007/240901

Full traceability context with production location and harvest date for food safety compliance.

How AIs Flow Through Resolution

When GTIN1 receives a Digital Link URI with qualifier AIs:

  1. The primary key AI (01) identifies the product via GTIN lookup.
  2. Each qualifier AI is parsed and validated against its format specification.
  3. Valid qualifiers are forwarded to the destination page as query parameters (e.g., ?lot=LOT2024A&serial=SN00001).
  4. The resolver rules system uses batch and serial context to select scope-specific rules when available.
  5. The product page renders content appropriate to the qualifier context -- for example, showing traceability events for a specific lot.