Historically, immigration officials were empowered to permit or reject entry of visitors on arrival at the frontiers. If permitted entry, the official would issue a visa, when required, which would be a stamp in a passport. Today, travellers wishing to enter another country must often apply in advance for what is also called a visa, sometimes in person at a consular office, by post, or over the Internet. The modern visa may be a sticker or a stamp in the passport, an electronic record of the authorization, or a separate document which the applicant can print before entering and produce on entry to the visited polity. Some countries do not require visitors to apply for a visa in advance for short visits.

Visa applications in advance of arrival give countries a chance to consider the applicant's circumstances, such as financial security, reason for travel, and details of previous visits to the country. Visitors may also be required to undergo and pass security or health checks upon arrival at the port of entry.

Some polities which restrict emigration require individuals to possess an exit visa to leave the polity.[2] These exit visas may be required for citizens, foreigners, or both, depending on the policies of the polity concerned. Unlike ordinary visas, exit visas are often seen as an illegitimate intrusion on individuals' right to freedom of movement. The imposition of an exit visa requirement may be seen to violate customary international law, as the right to leave any country is provided for in the Universal Declaration of Human Rights.