Tennis service order and change of ends
Understand alternating service, doubles rotation and the difference between changing server and changing court ends.
Standard games alternate service
At the end of a standard game, the receiver becomes the server and the server becomes the receiver for the next game. That change does not depend on who won the game. A break of serve wins a return game; it does not give the winner the next service game automatically.
Keep the serve marker separate from the games won. A player can lead in games while their opponent is serving, and a service change does not mean the set has ended.
Doubles keeps a rotation
In doubles, the team serving first chooses which partner starts that set. The other team chooses its server for the second game. The first team's other partner serves the third, and the second team's other partner the fourth; the rotation continues.
The receiving team also chooses which player receives the opening point in its first receiving game, with the partners alternating receiving positions according to the rules. Do not assume the more familiar player serves every important game.
Ends and service are different changes
Under the standard ITF change-of-ends rule, players switch at the end of the first, third and subsequent odd games of a set, with further provisions at set endings. Standard tie-breaks use a points-based change-of-ends pattern; alternatives exist.
A court-end switch and a server switch answer different questions. Read the game score, serve marker and format together on ScoreZaap. If a competition uses an alternative tie-break or scoring method, check its conditions before applying the standard pattern to every phase.