This document specifies the requirements of a performance indicator for libraries and establishes a set of indicators to be used by libraries of all types. It also provides guidance on how to implement performance indicators in libraries where such indicators are not already in use. This document is applicable to all types of libraries in all countries. However, not all performance indicators apply to all libraries. Limitations on the applicability of individual performance indicators are listed in the scope clause of the description of each indicator (see Annex A). This document provides a standardized terminology and concise definitions of the performance indicators. Furthermore, it contains detailed descriptions of the indicators and of the collection and the analysis of data needed. This document is not intended to exclude the use of performance indicators not specified in it.