Active Directory® Lightweight Directory Services (AD LDS) is a Lightweight Directory Access Protocol (LDAP) directory service in the Windows Server® 2008 R2 operating system that provides flexible support for directory-enabled applications, without the dependencies and domain-related restrictions of Active Directory Domain Services (AD DS). You can run AD LDS on member servers or stand-alone servers. You can also run multiple instances of AD LDS—each with its own independently managed schema—on one server.

AD LDS was previously called Active Directory Application Mode (ADAM). Under that name, it was available in Windows Server 2003 R2. It is also available as a separate download for Windows® XP Professional and Windows Server 2003.