IDs

An identifier, or ID, is a piece of data that uniquely identifies an item within a set. IDs are used to distinguish individuals, accounts, devices, documents, transactions, or other entities, and may be assigned by an organization or system. They can be numeric, alphanumeric, or follow structured formats, and may be stable over time or subject to revocation.

Common examples include government-issued identity documents such as passports or national identity cards, and government- or region-specific numbers like driver’s licenses or social security numbers. In computing and data systems, user IDs (usernames), account numbers, and database keys function as identifiers. In software development, universally unique identifiers or GUIDs/UUIDs provide globally distinct values, often used as primary keys.

IDs in databases often serve as primary keys, ensuring each row is unique and retrievable. They may be generated automatically, assigned by administrators, or created via standardized schemes. Some IDs incorporate check digits or formatting rules to detect entry errors, as in certain identification numbers and credit card schemes.

Handling and privacy: IDs can enable access control and auditing but also expose sensitive information. Best practices include limiting collection, protecting storage with encryption, applying access controls, using pseudonymization where possible, and avoiding unnecessary exposure in communications. Verification of identity typically relies on multiple attributes beyond a single ID.

Standards: some ID schemes are governed by standards, such as international identification card formats and software-related identifiers like UUIDs (RFC 4122). The term ID is broad and its exact meaning depends on context, including its scope, format, and governance.