Conformant and certified sound interchangeable and are not, and the difference matters when you are choosing infrastructure your packs will depend on for a decade. Precision here is a service to buyers, so this article defines both terms and shows how to verify each claim.
Conformance: a property of behaviour
The GS1-Conformant Resolver Standard specifies how a resolver must behave: correct content negotiation, linkset responses per RFC 9264, honest status codes, CORS, the resolver description file at its well-known address. Conformance means the running service matches that specification, and it is objectively checkable: GS1 publishes a test suite, and anyone can run it against any resolver, today, without permission. It is a property you verify, not a badge you are granted.
Certification: a relationship with a program
Certification and partner programs are organizational: membership, review processes, fees, logo rights. They have real value, procurement teams like them, and they are also distinct from the technical question, since a program member could run a nonconformant service and a non-member a flawless one. When a vendor says certified, the diligence question is: by which program, covering what, verified how, and does the running service also pass the technical suite?
How Onpack words its own claim, and why
Onpack claims conformance and shows its work: all checks of GS1's public resolver suite pass in continuous testing, meaning every deployment re-verifies the behaviours, and the footer states explicitly that GS1 does not endorse the service. That wording is deliberate. The trademark belongs to GS1; the behaviour belongs to whoever implements it correctly; and buyers deserve claims phrased so they can be checked, which is the same standard the resolver selection guide applies to everyone.
The five-minute verification, for any resolver
Request a product as JSON-LD and check structured data comes back. Request linkType=linkset and check the RFC 9264 document. Request a malformed identifier and expect 400, an unknown one and expect 404, never an error inside a 200. Fetch /.well-known/gs1resolver. Then, if the stakes justify it, run the full suite. Behaviour is the ground truth; everything else is marketing, ours included.
Common questions
What does GS1-conformant mean concretely?
That the resolver's behaviour matches the GS1-Conformant Resolver Standard, verifiable by running GS1's published test suite against it: content negotiation, linksets, errors, description file and the rest.
Is there an official GS1 certification for resolvers?
GS1 operates partner and certification programs whose membership is separate from technical conformance. A service can pass every technical check without being a program member, and vice versa.
How can I verify a conformance claim myself?
Run the public suite against the resolver, or spot-check by hand: request JSON-LD, request the linkset, request a bogus GTIN and watch the status codes.
Does Onpack claim certification?
No. Onpack claims conformance, passing all checks of the public suite in continuous testing, and says exactly that; it does not claim GS1 endorsement or program membership.