What Is a Product Identifier?
A product identifier is a code that distinguishes one product, trade item, catalog record or inventory item from another. Some are built for global trade; others exist only inside a single retailer, manufacturer or marketplace catalog.
- GTINIdentifies trade items through a global standards system.
- UPC / EANCommonly used barcode representations within the GTIN system.
- ASINIdentifies a product record inside Amazon's catalog.
- SKUIdentifies an item inside a specific company's inventory system.
- MPNIdentifies a manufacturer-defined product or part.
The same physical product can therefore have several identifiers at the same time.
The Core Product Identifier Types
GTIN
Global standard
Global Trade Item Number
GTIN is the umbrella standard for identifying trade items globally. It covers the GTIN-8, GTIN-12, GTIN-13 and GTIN-14 formats — the length depends on the product and its packaging context.
GTIN is the family. UPC and EAN are common formats within it.
EAN
Global standard · GTIN-13
European Article Number
EAN is the everyday European term for the 13-digit barcode identifier now represented in the GTIN system as GTIN-13.
For marketplace workflows, an EAN-13 can be treated as a GTIN-13 representation.
UPC
Global standard · GTIN-12
Universal Product Code
UPC is commonly used in North America. The standard UPC-A code contains 12 digits and fits within the GTIN system as GTIN-12. It can also be represented in a 13-digit context by adding a leading zero.
- UPC-A
- 012345678905
- GTIN-13 representation
- 0012345678905
Some identifier conversions are pure formatting operations.
ASIN
Amazon catalog
Amazon Standard Identification Number
An ASIN is Amazon's own catalog identifier — typically ten alphanumeric characters in the form B0XXXXXXXX. It points at an Amazon catalog entity rather than a global trade item, and a single product can carry a GTIN, a UPC or EAN representation and an ASIN at the same time.
ASIN to GTIN is a matching problem, not a conversion formula.
SKU
Internal inventory
Stock Keeping Unit
A SKU is created by a retailer, seller or company for its own inventory. SKUs are not standardized, so the same product can carry completely different SKUs in your ERP, at a retailer, at a distributor and inside a marketplace account.
- Your SKU
- SHOE-BLK-42
- Retailer SKU
- 9823417
A SKU identifies something inside a system. It does not identify it globally.
MPN
Manufacturer catalog
Manufacturer Part Number
An MPN is assigned by the manufacturer and is common in electronics, industrial products, spare parts, appliances and automotive components. A marketplace may expose a GTIN, a brand and an MPN for the same product.
An MPN supports matching. It does not replace a GTIN.
How GTIN, EAN, UPC, ASIN, SKU and MPN Relate
Global trade identity
- GTIN
- GTIN-12 / UPC
- GTIN-13 / commonly called EAN
- GTIN-8
- GTIN-14
Catalog and organization identity
- ASIN · Amazon catalog
- SKU · retailer / seller system
- MPN · manufacturer
All point toward
Product identity
The common mistake is treating every identifier as another representation of the same global code. UPC and EAN sit within the GTIN system, but ASIN, SKU and MPN come from different catalogs — so the system often has to work out whether two identifiers really point at the same product.
Identifier Conversion and Product Matching Are Different Problems
Identifier normalization
- UPC-A 012345678905step
- add leading zerostep
- GTIN-13 0012345678905result
Same identifier system. The representation changes predictably.
Product matching
- ASIN B0XXXXXXXXstep
- Amazon catalog recordstep
- GTIN / brand / MPN / variantstep
- candidate product identityresult
Different identifier systems. The product relationship must be resolved.
Some transformations can be calculated — a UPC-A becomes a GTIN-13 representation by adding a leading zero. An ASIN cannot: the system has to determine which product the ASIN refers to and whether that product has a corresponding GTIN.
Can You Convert an ASIN to an EAN or UPC?
Sometimes you can find the corresponding identifier — but it is usually a lookup or matching process, not a direct conversion.
An ASIN identifies an Amazon catalog record; an EAN or UPC identifies the trade item through the GTIN system. If a reliable catalog exposes the GTIN behind the ASIN, the two can be linked. Common complications:
- 01The catalog record may not expose a GTIN
- 02The listing may represent a bundle or multipack
- 03The ASIN may represent a variant
- 04Catalog data can contain duplicates or inconsistencies
- 05The same underlying product can appear differently across regions
- 06Different package quantities can require different GTINs
- 07Marketplace records can change over time
ASIN to EAN is therefore not the same type of operation as UPC to GTIN normalization. In practice the flow looks like this:
- ASIN
- Retrieve Amazon product record
- Inspect GTIN / UPC / EAN / brand / MPN / variant context
- Validate candidate
- Resolved product identity
What Is a UPC or GTIN Used for on Amazon?
Amazon runs on its own ASIN catalog, but products can also carry global trade identifiers such as UPCs, EANs or other GTIN formats.
- 01Identify products
- 02Create or associate catalog listings
- 03Distinguish packaging or variants
- 04Map external catalogs to Amazon records
Not every Amazon product exposes a usable UPC or EAN publicly, and an ASIN does not always correspond to exactly one global identifier.
ASIN tells you the Amazon catalog record. GTIN tells you the trade item identity.
Why Product Matching Gets Hard in Real Catalogs
A simple identifier lookup sounds deterministic. Production catalogs are not always that clean.
Variants
A product family may contain size variants, color variants, storage capacities or pack sizes. Matching only on the title can resolve the wrong variation.
Bundles and multipacks
A single unit and a 3-pack may share most product attributes while representing different trade items. They should not automatically be treated as equivalent.
Duplicate marketplace records
Marketplaces can contain multiple catalog records that appear to describe the same underlying product.
Regional catalog differences
A product can be represented differently across marketplace countries or regions.
Missing identifiers
Some marketplace records may not expose a usable GTIN. Matching then requires additional evidence.
Bad catalog data
Source data itself can be incomplete or inconsistent, so the matching layer has to handle uncertainty rather than assume clean inputs.
Four Properties of Reliable Identifier Matching
01
Explicit match confidence
A production system should not treat every candidate match as equally certain. The result should communicate how strong the identity evidence is, so downstream systems can decide what to trust.
A match without confidence hides uncertainty from the system that consumes it.
02
Variant and bundle awareness
Matching should distinguish between the product family and the exact variant — single item, multipack, bundle, different size or capacity. A technically similar product is not necessarily the correct trade item.
03
Explicit no-match behavior
A reliable system must be able to report that no reliable match was found rather than forcing the closest candidate into the result. No-match is a valid production outcome.
A wrong match is often more dangerous than no match.
04
Consistency across sources
Matching logic should produce predictable identity semantics across Amazon, Google Shopping, Walmart, Idealo, eBay, retailer marketplaces and other supported sources. Downstream systems should not have to invent a different identity model per source.
Related
Marketplace Data QualityWhy a Static ASIN-to-EAN Lookup Table Is Not Enough
A mapping table captures one moment in time. Marketplace catalogs keep moving after that snapshot is taken.
A static table answers
- The identifier a record carried when the snapshot was taken.
- A starting point for backfilling missing codes.
- Historical context for products that rarely change.
It cannot answer
- Whether the catalog record still exists today.
- Whether the listing was merged, split or relisted.
- Which variant or pack size the record now represents.
- Whether the identifier still resolves in this marketplace region.
Static mappings stay useful as context. When the current marketplace state drives a decision, the identifier has to be resolved against the live catalog.
What Should a Product Identifier API Actually Return?
Returning another identifier is rarely enough. A useful product-identity result carries the evidence behind the match as well.
Field
Meaning
input_identifier
The identifier you sent, unchanged.
normalized_identifier
The same identifier in its canonical GTIN representation.
source_product_id
The resolved catalog entity on the marketplace.
title
The product title as the source records it.
brand
Brand attribution used as matching evidence.
mpn
Manufacturer part number where the source exposes one.
variant_context
Size, color, capacity or pack size that separates near-identical items.
source_url
Reference back to the marketplace record.
match_confidence
How strong the identity evidence is.
resolution_status
Resolved, ambiguous or no reliable match.
The objective is not simply UPC to ASIN. It is getting from a customer product to the correct marketplace entity — the entity everything downstream depends on.
Prices · Offers · Sellers · Availability · Monitoring · Analytics
Related
Marketplace Data APIThe Wrong Product Makes Every Price Wrong
A technically perfect price extraction is useless if it belongs to the wrong product.
Same price extraction, two identities
Resolved correctly
- Input product
- Identity resolution
- Marketplace product
- Price / offers / sellers / availability
- Business decision
Resolved incorrectly
- Wrong match
- Perfectly extracted price
- Wrong competitor observation
- Wrong downstream decision
Identity is therefore part of marketplace data quality, not a separate concern that can be resolved afterwards.
How kwery Uses Product Identifiers
kwery treats product identity as the starting point for every marketplace observation. Depending on the source and the workflow, the input can be a GTIN, EAN, UPC or ASIN, a source-native identifier or a marketplace URL — the accepted identifiers per marketplace are listed in the API documentation.
Resolution path
- Customer product
- Identifier or product context
- kwery product resolution
- Matched marketplace entity
- Match and quality context
- Fresh marketplace observation
- Prices / offers / sellers / availability
kwery resolves the product first, then observes the marketplace.
The goal is not a generic barcode-conversion service. It is identifying the correct marketplace product before the observation is used downstream.
Product Matching Belongs Before Your Pricing Logic
There is a clean line between resolving which product you are looking at and deciding what to do about it.
kwery resolves
- Which marketplace entity your product maps to
- How strong the identity evidence is
- When no reliable match exists
- What the marketplace currently shows
- Which quality and provenance context travels with the observation
Your logic decides
- What price you set
- Which competitor matters
- What margin you require
- How your repricer behaves
- Which business rule wins
kwery enriches the observation. It does not own the decision.
Product Identifier Quick Reference
- 01
GTIN
Assigned by
GS1 / brand owner
Scope
Global trade item
Global?
Yes
Format
8, 12, 13 or 14 digits
GTIN conversion?
Already a GTIN
Primary use
Global product identity
- 02
EAN
Assigned by
GTIN system
Scope
Trade item
Global?
Yes, within GTIN
Format
13 digits commonly
GTIN conversion?
As GTIN-13
Primary use
European retail barcode
- 03
UPC
Assigned by
GTIN system
Scope
Trade item
Global?
Yes, within GTIN
Format
12 digits
GTIN conversion?
Normalizes to a GTIN
Primary use
North American retail barcode
- 04
ASIN
Assigned by
Amazon
Scope
Amazon catalog
Global?
No
Format
10 alphanumeric characters
GTIN conversion?
No universal formula
Primary use
Amazon catalog identity
- 05
SKU
Assigned by
Retailer / seller / company
Scope
Internal inventory
Global?
No
Format
Custom
GTIN conversion?
No
Primary use
Stock management
- 06
MPN
Assigned by
Manufacturer
Scope
Manufacturer catalog
Global?
No universal format
Format
Manufacturer-specific
GTIN conversion?
No
Primary use
Part and product identity
| Identifier | Assigned by | Scope | Global? | Format | GTIN conversion? | Primary use |
|---|---|---|---|---|---|---|
| GTIN | GS1 / brand owner | Global trade item | Yes | 8, 12, 13 or 14 digits | Already a GTIN | Global product identity |
| EAN | GTIN system | Trade item | Yes, within GTIN | 13 digits commonly | As GTIN-13 | European retail barcode |
| UPC | GTIN system | Trade item | Yes, within GTIN | 12 digits | Normalizes to a GTIN | North American retail barcode |
| ASIN | Amazon | Amazon catalog | No | 10 alphanumeric characters | No universal formula | Amazon catalog identity |
| SKU | Retailer / seller / company | Internal inventory | No | Custom | No | Stock management |
| MPN | Manufacturer | Manufacturer catalog | No universal format | Manufacturer-specific | No | Part and product identity |
For how these identifiers travel through a production data layer, see the ecommerce data guide.