The purpose of the ISOO CUI (Controlled Unclassified Information) Registry is to provide uniform definitions and responsibilities for CUI for every government agency that might come into contact with it, along with contractors that work with them. The registry identifies all approved CUI categories and subcategories, provides general descriptions for each, identifies the basis for controls, establishes markings, and includes guidance on handling procedures. It is a government-wide online repository for federal-level guidance regarding CUI policy and practice. The ISOO CUI Registry ensures that stakeholders follow DoD Instruction 5200.48, implements the NIST SP 800-171 framework, and meets CMMC (Cybersecurity Maturity Model Certification) requirements for DoD compliance. The DoD CUI registry exists independently from the ISOO registry but is nearly identical to it, and it includes all of the CUIs categories except Immigration, and it stipulates additional rules and responsibilities pertinent to DoD personnel and contractors.