ARF
The ARF, the Architecture and Reference Framework, is the technical specification of the EUDI Wallet ecosystem: it turns what eIDAS 2.0 requires in law into the concrete roles, credential formats, protocols and trust infrastructure that implementers have to build.
It is maintained by the European Commission together with the member states and published in versioned releases, each accompanied by a set of technical specifications for individual topics. The ARF is what settles the questions a regulation deliberately leaves open: that a wallet uses OpenID4VCI to receive credentials and OpenID4VP to present them, that PID and attestations come in SD-JWT VC and ISO mdoc format, how a wallet proves it is genuine, and how registered issuers and relying parties are published so the other side can check them. Anyone building for the EUDI Wallet reads the ARF rather than the regulation for these details, and the large-scale pilots test their implementations against it.