With the transition period over, freedom of movement between the UK and the EU member states also ended as the clock stroke midnight in Brussels.
Under the last-minute post-Brexit deal, British citizens will be able to visit most EU states as well as Iceland, Liechtenstein, Switzerland and Norway without a visa for up to 90 days in any 180-day period, but they will have to prove they have enough money for their stay. They will also need to show their return or onward ticket at the entry.
EU citizens will also have the same right when they want to visit to the UK.
British citizens planning to move to EU countries after Jan. 1 will apply for residency in line with member states' immigration rules as the automatic right to live and work in the EU ended.
Gibraltar, a British Overseas Territory, will be treated as a Schengen area according to an agreement reached by Spain and the UK.
As the UK and EU signed a post-Brexit trade before January 1, trade is expected to continue uninterrupted.
On December 24, European Commission President Ursula von der Leyen and the UK prime minister, Boris Johnson, announced that they had reached a deal on the future relations between the EU and the UK. The parties have thus managed to prevent the introduction of the World Trade Organization's rules, including customs tariffs and full border checks for goods flowing across the English Channel.