ORCID and ISNI are separate organizations that address different aspects of unambiguously identifying people and parties. The background, context and goals of each organization are distinct.
ORCID exists to solve the problem of accurate attribution of scholarly research output to individual researchers. ORCID is committed to allowing individual researchers to create, claim, manage and control the visibility of their data or to optionally delegate the management of their data to their university or another third party.
Because ORCID and ISNI have different purposes and serve different communities, both organizations are necessary. The organizations each hold different data, have different privacy and ownership rules for data, have different business models, and offer different services. Most importantly of all, ISNI and ORCID identify different things for different communities.
ORCID is built on a foundation of collaboration amongst publishers, universities, funding bodies, researchers, and other stakeholders in scholarly communications, and as such we are committed to interoperability with other identifier schemes, including ISNI.
Over the years, ORCID and ISNI have coordinated efforts where they overlap in the research and scholarship communities. ORCID identifiers utilize a format compliant with the ISNI ISO standard, and to ensure there will be no overlaps in assignments, ISNI reserved an initial block of identifiers for use by ORCID when we launched the ORCID registry in 2013. The first range of identifiers was defined between 0000-0001-5000-0007 and 0000-0003-5000-0001.
Fast forward to 2023. The ORCID registry has grown, now with over 16 million records, which means we required a new block of identifiers. This new range reserved for ORCID by ISNI is defined between 0009-0000-0000-0000 and 0009-0010-0000-0000.
These blocks of numbers mean that ORCID use them without any concern of conflict with ISNI. There is no relationship between these numbers that ISNI have set aside and ORCID other than that. ORCID is a completely separate identifier from ISNI, therefore it is entirely possible that someone may have both an ISNI and an ORCID and use them for different use cases.