Fault vs Double Fault in Tennis: What's the Difference?

Every service point in tennis carries a small built-in safety net: you get two chances to start it. Understanding what turns one missed serve into a lost point is the difference between watching tennis and actually following the pressure a server feels on a second delivery.

What a fault is

A fault is a serve that fails to count. The most common cause is the ball missing the correct service box, either landing long, wide, or in the net. When that happens on your first serve, nothing bad happens yet. You simply get a second serve.

A serve can be a fault for reasons beyond where the ball lands:

• The ball lands outside the correct service box.
• The ball hits the net and lands outside the box (if it clips the net and lands in, that is a let, not a fault).
• The server commits a foot fault by stepping on or over the baseline before contact.
• The server misses the ball completely while trying to hit it (in most rulings a whiffed toss they swing at counts as a fault).

What a double fault is

A double fault is two faults on the same point. Miss the first serve, then miss the second, and the point is over. It goes straight to the receiver with no rally. This is why the second serve is one of the most pressured shots in the sport: there is no third chance.

Because of that pressure, most players hit a safer, spin-heavy second serve rather than risk a big flat delivery twice. A cautious second serve trades some free power for a much lower chance of handing away the point.

Fault vs double fault at a glance

Foot faults explained

Foot faults trip up club players more than they realize. Before striking the ball, the server must keep both feet behind the baseline and inside the imaginary extensions of the sidelines and center mark. Touching the line early, or the court beyond it, is a foot fault and is treated exactly like any other fault. At the professional level line officials or electronic systems watch for this closely.

Why the two-serve system exists

Giving servers two attempts keeps rallies alive and rewards aggressive first serves without punishing every small miss. It is a balance: the first serve can be a weapon, and the second is the insurance. A player’s second-serve reliability often tells you more about their nerve than their flashiest winners.

If you are new to tennis scoring, faults sit alongside a few other must-know serve terms. Learn how a clean, unreturnable serve becomes an ace, and the full picture of what can happen on a single serve starts to come together.