Identity (ID) cards are in use in one form or another in virtually all countries of the world. The type of card, its function, and its integrity vary enormously. While a majority of countries have official, compulsory, national IDs that are used for a variety of purposes, many developed countries do not have such a card. Amongst these are the United States, Canada, New Zealand, Australia, the United Kingdom, Ireland, and the Nordic countries. Those that do have such a card include Germany, France, Belgium, Greece, Luxembourg, Portugal and Spain

ID cards are established for a variety of reasons. Race, politics and religion were often at the heart of older ID systems. The threat of insurgents, religious discrimination or political extremism have been all too common as motivation for the establishment of ID systems which would force enemies of the State into registration, or make them vulnerable in the open without proper documents. In Pakistan, the cards are used to enforce a quota system

In recent years, ID cards have been linked to national registration systems, which in turn form the basis of government administration. In such systems - for example Spain, Portugal, Thailand and Singapore - the ID card becomes merely one visible component of a much larger system. With the advent of magnetic stripes and microprocessor technology, these cards can also become an interface for receipt of government services. Thus the cards become a fusion of a service technology, and a means of identification. At the heart of such plans is a parallel increase in police powers. Even in democratic nations, police retain the right to demand ID on pain of detention. In a number of countries, these systems have been successfully challenged on constitutional privacy grounds. In 1998, the Philippine Supreme Court ruled that a national ID system violated the constitutional right to privacy. In 1991, the Hungarian Constitutional Court ruled that a law creating a multi-use personal identification number violated the constitutional right of privacy

Maintaining every citizen's ID card on a central system imperils any attempt to maintain its confidentiality because of its availability on the screens of social security, police and immigration offices, before taking into consideration bribery and the theft of commercially valuable information. Once compulsory, showing such cards becomes the norm in many circumstances beyond that required by the law. Such cards are therefore invasive, subject to inexactitude, open to manipulation and an infringement of personal freedoms

Compulsory identity cards are an appropriate response to crime, uncontrolled immigration and social security fraud