The system involves registering personal and biometric data in advance digitally, through an application, and paying a fee of £10 (€12).
The authorisation may take up to three days and will be valid for two years, during which time multiple visits to the United Kingdom of up to six months in length may be made.
After an experimental phase with some Arab countries that began in 2023, the system will be extended to all visitors who do not require a prior visa for short stays.
Visitors from non-European countries such as the United States, Brazil, Macau or Argentina will be able to apply from 27 November and will need to have an Electronic Travel Authorisation (ETA) from 8 January.
European tourists, including those from Portugal, will be able to apply from 5 March, and it will be mandatory for anyone who is visiting the UK from 2 April 2025.
British nationals living abroad, as well as foreign nationals living in the Republic of Ireland, are exempt as they are part of a common travel area with the UK.
The ETA may be rejected on the grounds of a criminal record or risk, for example, of terrorism.
The British Home Office said that this measure is part of the aim to digitalise the UK’s border and immigration system.
“Digitalisation enables a smooth experience for the millions of people who cross the border every year,” said Home Secretary Seema Malhotra.
This system does not apply to holders of residence permits, such as those registered in the EU Settlement Scheme (EUSS) opened after Brexit, workers with visas or students.
The UK system is similar to those used by countries such as the US, Canada, Australia and New Zealand and to the European Travel Information and Authorisation System (ETIAS) which the EU aims to have in place by the first half of 2025.