A resolver is a component that takes an identifier and returns the resource, address, or value it stands for. In identification infrastructure such as GS1 Digital Link and the Domain Name System, a resolver service receives a request containing a structured identifier and redirects the requester to one of potentially many linked resources — product information, traceability records, or network addresses — chosen by link type and context. The term also names the electromechanical rotary transformer used in robotics and motor control to resolve a shaft’s absolute angular position from induced analogue signals.
Semantic Classification
Content
Definition
A resolver performs indirection: given an identifier, it answers the question “what does this stand for, right now, for this requester?” The pattern recurs wherever identification is separated from location. The Domain Name System resolver maps a host name to an IP address; a DID resolver maps a decentralised identifier to its DID document; and in the GS1 ecosystem a Gs1 Digital Link resolver maps a product identifier embedded in a web URI to the set of online resources associated with that product.
In the GS1 Digital Link architecture (ISO/IEC 18975 covers the resolution mechanism), scanning a QR code on a product yields a URI such as https://id.example.com/01/09506000134352, where 01 introduces the Global Trade Item Number. The resolver hosted at that domain inspects the identifier and any qualifiers (batch, serial number) together with requested link types — gs1:pip for product information, gs1:traceability for provenance, gs1:recallStatus, and so on — and issues an HTTP redirect to the appropriate destination. One physical data carrier can therefore serve consumers, regulators, recyclers, and supply-chain partners with different resources, and brand owners can change destinations without reprinting packaging. This late binding is what makes resolvers the linchpin of Interoperability between physical products and the web, including EU Digital Product Passport architectures.
The same word names an unrelated but equally established device: the electromechanical resolver, a rotary transformer used as an absolute angle sensor. A reference winding excited with an AC signal induces voltages in two stator windings arranged at 90°, proportional to the sine and cosine of the shaft angle; a resolver-to-digital converter recovers the angle from the ratio. Because the device is brushless, contactless, and contains no electronics at the point of measurement, it tolerates heat, vibration, and radiation that would destroy optical encoders, which is why it appears as a component of the Proprioceptive Sensor suite in industrial robots, servo drives, and aerospace actuators, alongside the Rotary Encoder it competes with.
Technical Details
Identifier resolvers share a common design vocabulary: a well-known entry point (DNS roots, /.well-known/gs1resolver description files), a syntax for decomposing the identifier, a link registry mapping identifiers and link types to destinations, and content negotiation so that humans receive web pages while machines receive structured data (JSON-LD linksets per RFC 9264). Operational concerns mirror DNS: caching and TTLs, redundancy and anycast deployment for availability, and governance over who may write entries for a given identifier range. GS1 operates a global resolver at id.gs1.org, with brand owners able to delegate resolution for their own prefixes to private resolvers — a federated model deliberately analogous to DNS zone delegation.
Current Landscape
-
Standardisation (2025): GS1 published Digital Link URI syntax 1.6.0 (April 2025) and the GS1-Conformant resolver 1.1.0 (February 2025); the underlying resolution mechanism is now an international standard, ISO/IEC 18975 (“encoding and resolving identifiers over HTTP”), which formally defines a resolver as a service that accepts a conformant URI and redirects to the relevant target resource from a linkset.
-
Conformance levels: the GS1 framework grades resolvers Level 0 (basic HTTP redirect) → Level 1 (content negotiation) → Level 2 (full linkset API for machine discovery, per RFC 9264) → Level 3 (compressed Digital Link URIs); Level 1–2 is recommended for Digital Product Passport use.
-
EU Digital Product Passport: under the ESPR, the resolver is the pivot that turns a scanned GS1 Digital Link URI into DPP data via the
gs1:digitalProductPassportlink type; importantly, the ESPR mandates a unique identifier and data carrier but stays technology-neutral and does not name GS1 Digital Link as the sole mandatory standard. -
Adoption timeline: industry “2D barcode / GS1 Digital Link” migration plans target 2027 at retail point-of-sale, driving resolver deployment; the DPP requirement that passport data stay accessible for years after sale makes persistent, well-governed resolver infrastructure a hard requirement.
-
Electromechanical resolvers remain a distinct, mature technology — brushless absolute angle sensors prized in aerospace, servo drives and industrial robotics for tolerance to heat, vibration and radiation.
Sources:
-
https://gs1.eu/wp-content/uploads/2025/04/GS1-Standards-Enabling-DPP-V2.2.pdf
-
https://myproductpassport.eu/blog/gs1-digital-link-resolver-how-it-works