Uefa has confirmed that countries will be able to name 26-man squads for this summer's Euro 2020.
Squads for the tournament will be able to include three more players than usual in case of positive tests for Covid-19 and subsequent spells of quarantine.
France and Belgium managers Didier Deschamps and Roberto Martinez were among those who had called for the change while England's Gareth Southgate had been opposed. Match-day squads will still be limited to 23 players.
European football's governing body also confirmed that coronavirus was classed as a "serious illness", meaning a player can be replaced if he tests positive before a team's first match.
The tournament, which had been scheduled to take place last summer, begins on 11 June. The deadline for submitting squads is 1 June.
Uefa said in a statement: "To mitigate the risks of teams facing a shortage of available players for certain matches due to possible positive Covid-19 tests results and subsequent quarantine measures ordered by competent authorities, it has been decided to exceptionally increase the player list for all participating teams to 26 players.
"However, 23 players shall remain the maximum number permitted on the match sheet for each individual match ... including three goalkeepers.
Gallery: Scotland celebrate Euro 2020 qualification
"For the sake of clarity, players who have tested positive for Covid-19 or who have been declared as 'close contacts' of a positive Covid-19 tested person – and therefore put in isolation – by way of an authorities' decision are considered cases of serious illness and can therefore be replaced before the first match with the approval of the Uefa administration."
Uefa said goalkeepers would be able to be called up in case of injury or illness before each match, even if one or two keepers from the player list are still available.
A player that has been replaced on the player list will not later be allowed to return to the competition.
Uefa had already decided that teams would be allowed to make up to five substitutions in games at the delayed tournament instead of the usual three, in line with current rules across many club competitions.
Euro 2020 was postponed last year because of the pandemic but is due to take place at venues across the continent, from June 11 to July 11.
It was set to be held in 12 hosts cities in 12 countries but Dublin and Bilbao were forced to drop out as they could not guarantee the presence of fans at the Aviva Stadium in the Irish capital and the San Mames.
The four matches due to be held in the Basque Country – three from Group E and a last 16 game – were kept in Spain by moving them to Seville's La Cartuja stadium.
The three Group E matches originally scheduled to be held in Dublin were shifted to Saint Petersburg, which had already been assigned three Group B matches and a quarter-final, while London's Wembley Stadium took the last 16 match.
Gallery: England beat Kosovo in final Euro 2020 qualifier
