Each country playing at Euro 2020 this summer will be allowed a squad of 26 and will be able to replace players who test positive for Covid-19 up until their first match.
UEFA has confirmed the increase in squad numbers from the usual 23 players to 26 in light of the tournament being played in extraordinary circumstances amid the pandemic.
The expanded squads will ease the situation if one or more players within the camp test positive for coronavirus and have to self-isolate during the finals, which begin on June 11.
UEFA confirmed, however, that only 23 players can be selected for each individual match, with the other three not included on the teamsheet.
That is because the laws of the game state that a maximum of 12 substitutes are permitted for top level international matches.
But in a further easing of the rules, UEFA will permit national team managers to make unlimited replacements of players within the 26-man squad right up until their first fixture.
That means if a player is injured or falls ill after the squads are submitted on June 1, there is a window within which they can be replaced by someone else.
The new rules also allow goalkeepers in the squad to be replaced throughout the tournament if they test positive for Covid-19.
But once a player has been taken out of a squad, they cannot then be readmitted.
Teams will be able to make five substitutions during matches at the tournament.
The 24-team tournament gets underway when Italy play Turkey at the Stadio Olimpico in Rome on June 11. The final takes place at Wembley Stadium in London on July 11.
Euro 2020 Schedule
Friday 11 June
Group A: Turkey vs Italy (21:00, Rome)
Saturday 12 June
Group A: Wales vs Switzerland (15:00, Baku)
Group B: Denmark vs Finland (18:00, Copenhagen)
Group B: Belgium vs Russia (21:00, St Petersburg)
Wednesday 16 June
Group B: Finland vs Russia (15:00, St Petersburg)
Group A: Turkey vs Wales (18:00, Baku)
Group A: Italy vs Switzerland (21:00, Rome)
Thursday 17 June
Group C: Ukraine vs North Macedonia (15:00, Bucharest)
Group B: Denmark vs Belgium (18:00, Copenhagen)
Group C: Netherlands vs Austria (21:00, Amsterdam)
Friday 18 June
Group E: Sweden vs Slovakia (15:00, Dublin)
Group D: Croatia vs Czech Republic (18:00, Glasgow)
Group D: England vs Scotland (21:00, London)
Saturday 19 June
Group F: Hungary vs France (15:00, Budapest)
Group F: Portugal vs Germany (18:00, Munich)
Group E: Spain vs Poland (21:00, Bilbao)
Sunday 20 June
Group A: Italy vs Wales (18:00, Rome)
Group A: Switzerland vs Turkey (18:00, Baku)
Monday 21 June
Group C: North Macedonia vs Netherlands (18:00, Amsterdam)
Group C: Ukraine vs Austria (18:00, Bucharest)
Group B: Russia vs Denmark (21:00, Copenhagen)
Group B: Finland vs Belgium (21:00, St Petersburg)
Tuesday 22 June
Group D: Czech Republic vs England (21:00, London)
Group D: Croatia vs Scotland (21:00, Glasgow)
Wednesday 23 June
Group E: Slovakia vs Spain (18:00, Bilbao)
Group E: Sweden vs Poland (18:00, Dublin)
Group F: Germany vs Hungary (21:00, Munich)
Group F: Portugal v France (21:00, Budapest)
The top two in each group plus four best third-placed teams go through.
Rest days on 24 and 25 June
Round of 16
Saturday 26 June
1: 2A vs 2B (18:00, Amsterdam)
2: 1A vs 2C (21:00, London)
Sunday 27 June
3: 1C vs 3D/E/F (18:00, Budapest)
4: 1B vs 3A/D/E/F (21:00, Bilbao)
Monday 28 June
5: 2D vs 2E (18:00, Copenhagen)
6: 1F vs 3A/B/C (21:00, Bucharest)
Tuesday 29 June
7: 1D vs 2F (18:00, Dublin)
8: 1E vs 3A/B/C/D (21:00, Glasgow)
Rest days on 30 June and 1 July
Friday 2 July
QF1: Winner 6 vs Winner 5 (18:00, St Petersburg)
QF2: Winner 4 vs Winner 2 (21:00, Munich)
Saturday 3 July
QF3: Winner 3 vs Winner 1 (18:00, Baku)
QF4: Winner 8 vs Winner 7 (21:00, Rome)
Rest days on 4 and 5 July
Tuesday 6 July
SF1: Winner QF2 vs Winner QF1 (21:00, London)
Wednesday 7 July
SF2: Winner QF4 vs Winner QF3 (21:00, London)
Rest days on 8, 9, 10 July
Sunday 11 July
Winner SF1 vs Winner SF2 (21:00, London)