At this summer’s European Championship, teams will be able to select a 26-player squad instead of the normal 23.
The move was made to lighten the pressure on players after a club season that was cut short due to the coronavirus pandemic.
It will also assist administrators in adapting in the event of an epidemic during the tournament.
The decision, which was made by Uefa’s national teams committee on Monday, would need to be ratified, although it is unlikely to face any resistance.
The decision will be ratified by Uefa’s governing executive committee later this week.
A rule allowing each team to substitute up to five players per game has already been verified.
The tournament, which was originally scheduled for last summer, will begin on June 11th. The deadline for squad submissions is June 1st.
Gareth Southgate, England’s boss, is scheduled to name his squad the week of May 24.
Scotland manager Steve Clarke will announce a provisional squad in mid-May before naming his final squad at the end of the month.
Following confirmation that he will be in charge of the team for the tournament, Robert Page will be in charge of selecting the Wales squad.