The most popular identifiers in use are ORCID, WoS ResearcherID and Scopus AuthorID, which can be integrated between each other. 

ResearcherID and AuthorID are proprietary IDs, as their usage is restricted to the access to proprietary databases. They both allow researchers to manage their publications’ lists as indexed in the two databases, keep track of the received citations, and monitor the h-index, avoiding mistakes in their identification.

ORCID Open Researcher and Contributor ID is a non-proprietary ID. All profiles are public and visible on a non-commercial platform, not bound to any specific database. It is a univocal, alphanumeric and persistent identifier, released by ORCID international, interdisciplinary and nonprofit organization, whose members are academic institutions, researchers and publishers. Participation to ORCID is allowed to every organization making research and scientific dissemination: single researchers, academic and research institutions, laboratories, research companies, publishers, and professional societies.

The service is open and free: every researcher is able to create, modify, and maintain his/her own ORCID ID, as well as set access conditions to their data. Data provided to ORCID are available for free download in standard formats. 

The aim of the organization is to create and maintain a register of univocal identifiers, enhancing the connection between scientific production, authors, affiliations, roles, research projects, and financing.