European football's governing body Uefa on Tuesday bowed to pressure from coaches and confirmed squads can be expanded from 23 to 26 players for this summer's European championships.
The tournament, postponed from last summer due to the coronavirus pandemic, starts on 11 June and will finish on 11 July.
"Uefa has agreed the increase to mitigate the risks of teams facing a shortage of available players for certain matches due to possible positive Covid-19 test results and subsequent quarantine measures," said a spokesperson.
National team managers have named squads of 23 players at the World Cup and European Championships since the 2002 World Cup in Japan and South Korea.
However, after a year during which scores of players have contracted the coronavirus, national team coaches such as France's Didier Deschamps and Belgium's Roberto Martinez have urged Uefa to consider larger squads.
Last year's Euro 2020 was promoted as a pan-European event to celebrate the 60th anniversary of the competition. A dozen cities in 12 countries had been lined up for the extravaganza.
A year on, Dublin and Bilbao have dropped out because they say they cannot carry out Uefa's wish to have fans in the stadiums.
The four matches due to be held at the San Mames in Bilbao - three from Group E and a last 16 game - have been kept in Spain but moved to Seville's La Cartuja stadium.
The three Group E matches scheduled for the Aviva Stadium in Dublin have been shifted to Saint Petersburg, which had already been assigned three Group B matches and a quarter-final. , London's Wembley Stadium twill accommodate the last 16 match.