The news was confirmed by Uefa, which also said that four cities – Dublin, Munich, Rome and Bilbao – would have until 19 April to confirm they will permit crowds or risk losing their right to host matches.
The other eight cities will have fans – although Budapest is the only one to commit to full stadiums for the tournament. Baku and St Petersburg will have an initial capacity of 50%, with the others between 25-33% for the group stages.
It means that England’s group matches at Wembley and the last-16 match will have 22,500 fans, although the Football Association is hoping the figure will at least double for the semi-finals and final.
Uefa has also indicated that cities will have until the end of April to increase the numbers of fans if they believe the vaccination rollout, and the projected slow-down in the virus in warmer weather, makes it safe to do so.
But European football’s governing body has warned fans wishing to travel that they “will find it challenging due to ever-changing restrictions” – which in most cases include having to quarantine.
Three cities – Budapest, St Petersburg and Baku – have, however, indicated they are willing to take fans from abroad to watch the games without such restrictions. This “special procedure” means that Wales fans can fly to the Switzerland and Turkey games, provided they hold a ticket and can present proof of a recent negative Covid-19 test.
Travel from Cardiff to the Baku Heydar Aliyev International is likely to take at least 15 hours and involve a minimum of three flights, unless there is a chartered plane.
Uefa also confirmed that fans with tickets for Euro 2020 games can return them for a full refund by 22 April. If the number of tickets sold for a match exceeds the permitted seating, a ballot will be held to decide who misses out.
Fans of Hungary, North Macedonia, Scotland and Slovakia – who qualified through play-offs – will be able to start buying tickets in early May.