The Lightweight Directory Access Protocol (LDAP) is a directory service protocol that runs directly over the TCP/IP stack. The information model (both for data and namespaces) of LDAP is similar to that of the X.500 OSI directory service, but with fewer features and lower resource requirements than X.500. Unlike most other Internet protocols, LDAP has an associated API that simplifies writing Internet directory service applications. The LDAP API is applicable to directory management and browser applications that do not have directory service support as their primary function. LDAP cannot create directories or specify how a directory service operates. or on the other word LDAP is a protocol for the querying of address directories on the Internet.

The Lightweight Directory Access Protocol (LDAP) (pronounced /ˈɛldæp/) is an application protocol for querying and modifying data of directory services implemented in Internet Protocol (IP) networks.

A directory is a set of objects with attributes organized logically in a hierarchical manner. A simple example is the telephone directory, which consists of a list of names (of either persons or organizations) organized alphabetically, with each name having an address and phone number associated with it.

A directory information tree often reflects various political, geographic, and/or organizational boundaries, depending on the model chosen. LDAP deployments today tend to use Domain Name System (DNS) names for structuring the topmost levels of the hierarchy. Deeper inside the directory might appear entries representing people, organizational units, printers, documents, groups of people or anything else that represents a given tree entry (or multiple entries).

The latest version of LDAP is Version 3, which is specified in a series of Internet Engineering Task Force (IETF) standard track Requests For Comments (RFCs) as detailed in RFC 4510.