What Is an Ace in Tennis? Definition and Why It Matters

An ace in tennis is a legal serve that lands in the correct service box and is not touched by the receiver, winning the point outright. The ball crosses the line, the returner reacts, and nothing happens: the point is over before a rally can start. It is the cleanest point on serve and one of the sport’s most valuable weapons.

The one-line definition of an ace

An ace is a serve that lands in and the receiver never touches. The moment the ball hits the correct service box untouched, the point belongs to the server. That “untouched” part is the whole difference between an ace and every other serve: any contact, even a graze off the frame, disqualifies it.

How an ace works

Three things have to line up for a serve to count as an ace:

1. The ball clears the net cleanly (a let does not count).
2. It lands inside the correct, diagonally opposite service box.
3. The receiver never touches it, not even a graze off the racket frame.

If all three hold, the umpire scores it as an ace. Touch the ball at all and it becomes either a service winner or a live point.

Ace vs. service winner

People use these two terms interchangeably, but they are not the same:

Term	Definition
Ace	Serve lands in; receiver does not touch the ball
Service winner	Serve lands in; receiver touches it but cannot return it in play

Both end the point fast, but only the ace means the returner never made contact. Broadcasts track them separately, so a player’s ace count is always lower than their total unreturned serves.

First serve vs. second serve aces

Aces happen off both serves, though the odds shift:

• First serve. Players swing harder and go for the corners, accepting more risk since a miss just means a second serve. The large majority of aces come from here.
• Second serve. Players ease off to avoid a double fault, so a second-serve ace is much rarer and usually means the server disguised the placement well or overpowered the return.

Why aces matter tactically

An ace is a free point: no energy spent, no chance for the returner to find rhythm. Over a best-of-five Grand Slam match, a server who racks up aces holds serve more efficiently, the difference between straight sets and a grinding fifth. There is a psychological side too: string together a few aces and the returner starts guessing where the next one is headed. A big server can even hold to love with four aces in one game.

Surfaces and aces

Court surface changes how often aces happen:

Surface	Bounce	Ace frequency
Grass	Low, fast	Highest
Hard	Medium	Moderate
Clay	High, slow	Lowest

Grass courts, Wimbledon being the obvious example, produce the most aces because the ball skids low and fast. Clay slows everything down and gives the returner more time to track the ball, so aces are scarcest there.

Ace records and the modern big servers

The players atop the all-time ace lists share a few traits: height, a fast arm, and precise placement. As of 2026, John Isner holds the ATP career record with roughly 14,470 aces, having passed Ivo Karlovic (near 13,700) in 2022. Roger Federer and Feliciano Lopez each cleared 10,000, and Serena Williams ranks among the women’s tour’s most prolific ace servers ever.

The modern era keeps pushing serve speeds higher. At Wimbledon 2025, France’s Giovanni Mpetshi Perricard hit a 153 mph serve, the fastest in tournament history, and led the ATP Tour in average first-serve speed that season. The fastest serve ever measured remains Sam Groth’s 263.4 km/h (163.7 mph) from 2012, while Isner’s 253 km/h (157.2 mph) at the 2016 Davis Cup is the fastest at an official ATP-level match. With a new wave of towering servers, both records look likely to keep climbing.

Related terms

• Service winner — a serve the receiver touches but cannot return in play.
• Double fault — two missed serves in a row, handing the point to the returner.
• Let — a serve that clips the net cord and lands in, which is replayed.
• Break point — a point on which the returner can win the server’s game, the situation an ace most dramatically erases.