Budapest is the only playing city that wants a full stadium during the European Football Championship next summer, UEFA announced on Friday.
The spectators in the Puskás Aréna have to meet strict "entry requirements".
What they are has not been disclosed.
According to Hungarian media, the Hungarian government only allows vaccinated people in the stadium, which seats 67,000 fans.
All Hungarians could have had an injection in June.
Three group matches and one game in the eighth finals of the tournament are scheduled in the Puskás Aréna.
This concerns the group matches Hungary-Portugal (June 15), Hungary-France (June 19) and Portugal-France (June 23).
The winner of group C plays against one of the four best numbers three in the last sixteen in the Hungarian capital.
The twelve playing cities of the European Championship had to inform UEFA by Wednesday whether and how many spectators could be welcome in the stadium.
At least twelve thousand people are welcome in the Johan Cruijff ArenA in Amsterdam at matches of the Dutch national team, the KNVB reported on Wednesday.
Stadium capacity European Championship host cities
Budapest (Puskás Aréna): 100 percent
Saint Petersburg (Krestovsky Stadium): 50 percent
Baku (Olympic Stadium): 50 percent
Amsterdam (Johan Cruijff ArenA): at least 25 percent
Glasgow (Hampden Park): at least 25 percent
Copenhagen (Parks): at least 25 percent
Bucharest (Arena Nationala): at least 25 percent
London (Wembley): at least 25 percent
Rome (Stadio Olimpico): unknown
Munich (Allianz Arena): unknown
Bilbao (San Mamés): unknown
Dublin (Aviva Stadium): unknown
Fans do not have to be quarantined in three countries
The Krestovsky Stadium in Saint Petersburg will be at least 50 percent full.
If the contamination figures in Russia allow it, more fans can enter the stadium.
The stadium will also be half occupied in the Azerbaijani capital Baku.
In Hungary, Russia and Azerbaijan, foreign fans are also exempt from quarantine rules.
Normally, foreigners have to be in isolation for a few days upon arrival in the three countries mentioned.
With a negative test they can now 'just' go on the street.
It was previously known that the host cities of Munich, Dublin, Rome and Bilbao could not yet give a definite answer about allowing an audience at the European Championship.
UEFA will give them until April 19 to submit a plan.
The European Championship, which has already been postponed for a year due to the corona virus, will be spread over twelve playing cities due to the fiftieth anniversary of the tournament and will start on 11 June.
The final will be played on July 11 at Wembley.
Portugal is the defending champion.
See also: Will it still be a European Championship in less than twelve countries?
These are the proposals