A ball skims the paint beside the doubles alley. Is it in, or is it out? The answer can flip with the format—and that tiny strip of court can turn a rally-winning shot into a fault. Get the boundary rules straight and you’ll stop second-guessing calls, understand why doubles players love the extra width, and know exactly when those alleys count.
The short version: a doubles court is wider than a singles court, but the extra space on each side is not part of the service box. The alleys are out when a serve lands in them, then in for the rest of a doubles rally. Here’s how the lines work in real play.
The court: same length, different width
Singles and doubles use the same court length and the same baseline. The difference is the sidelines: singles uses the narrower pair of lines, while doubles uses the wider pair. The strip between those two lines on each side is the doubles alley, also called the tramlines.
| Measurement or feature | Singles | Doubles |
|---|---|---|
| Court length | 78 ft (23.77 m) | 78 ft (23.77 m) |
| Court width | 27 ft (8.23 m) | 36 ft (10.97 m) |
| Side boundary for rallies | Inner sideline | Outer sideline |
| Doubles alley | Out | In during rallies |
Each alley is 4.5 feet (1.37 m) wide. Add one on either side of the singles court and you get the nine-foot difference between singles and doubles widths. The extra room is a big deal in doubles: it gives players more angles to work with and makes it harder for two opponents to cover the court together.
The lines themselves matter. A ball that touches a boundary line is considered in. So, in singles, a ball touching the inner singles sideline is good; a ball landing entirely beyond that line is out, even if it lands inside the painted alley. In doubles, the outer sideline is the rally boundary, and a ball touching that line is good.
When the doubles alleys are in play
In a doubles rally, the alleys are in. Once the serve has been put into play, either team can hit a shot that lands in the alley and win the point with it. A groundstroke down the outside lane, a sharp crosscourt angle, or a lob that drops near the outer sideline can all be legal, provided the ball lands on or inside the doubles court boundary.
In a singles rally, those same strips are out. The singles court ends at the inner sidelines, so a shot that lands in the alley is out—even if it looks close to the doubles line. Players sometimes train or warm up on a court with all the lines visible, which can make the boundary feel confusing. When in doubt, identify which format you’re playing and follow that format’s sideline.
A quick rally example
Imagine a doubles player is pulled wide and sends the ball down the line. If it lands between the singles sideline and the outer doubles sideline, it is in for doubles. Play continues. Now imagine the same shot during a singles match: that landing spot is outside the singles court, so the shot is out.
The player’s position doesn’t change the call. A singles player can run into the alley to reach a ball, but the ball still has to land inside the singles boundaries. Similarly, a doubles player can stand in the alley, and the alley remains part of the court during a rally.
The serve is the important exception
Here’s the detail that catches many new doubles players: the alleys are out when the serve lands. In both singles and doubles, a serve must land in the correct diagonal service box. That box is bounded by the center service line, the net, the service line, and the inner singles sideline—not the outer doubles sideline.
So a doubles server cannot aim at the alley as part of the service box. If the serve’s first bounce is in the alley, it is a fault. The same is true if the serve lands beyond the singles sideline or beyond the service line. Doubles gives the server and receiver a wider court for rallies, but it does not make the service target wider.
| Situation | Does the alley count? | What happens? |
|---|---|---|
| A serve’s first bounce lands in the alley | No | Fault |
| A doubles rally shot lands in the alley | Yes | Ball is in |
| A singles rally shot lands in the alley | No | Ball is out |
| A ball touches the relevant outer boundary line | Yes | Ball is in |
If a legal serve lands in the service box and then bounces or travels toward the alley, that doesn’t make the serve a fault. The crucial question is where the ball’s first bounce occurs. After that bounce, the rally rules apply: the alleys are in for doubles and out for singles.
That’s why a wide serve in doubles can be so useful without landing in the alley. The server can hit near the outside edge of the service box, forcing the receiver to stretch. A good return may then be directed into the alley, where it is a perfectly legal rally shot.
Why the wider doubles court changes tactics
Nine extra feet of width sounds generous, but it is shared across both sides of the court, and doubles players have to cover it together. The added space rewards smart angles and clear teamwork. A server may pull the receiver toward the sideline, while the net partner watches for a return up the middle or down the line. The receiver, meanwhile, has to judge whether a tempting alley shot is genuinely open or whether the opposing net player is waiting to intercept it.
The alley also changes recovery positions. In singles, a player who hits a wide shot often has to recover toward the middle of the narrower court. In doubles, the team’s positions are more specialized: one player may cover the baseline while a partner takes the net, and both need to communicate about who owns a ball headed toward the alley. The line may be in, but that doesn’t mean the shot is automatically wise. A low-percentage attempt close to the outer line can hand over a point if it misses.
One practical doubles habit: think of the alley as extra court, not as a separate target lane. Use it when the angle is there, but don’t force the ball toward the paint just because the space exists. A deep shot through the middle can be tougher for a pair to handle than a risky winner inches from the sideline.
How to read a court with both sets of sidelines
On a standard court, the singles and doubles sidelines are both marked, so it’s easy to mistake one for the other—especially when you’re moving quickly. Before play starts, take a moment to point out the boundary for your match. In singles, use the inner lines. In doubles, use the outer lines for rallies, but remember that the service-box sideline is still the inner singles line.
Some courts use different colors for different lines, and temporary courts may have markings that are less familiar. Don’t rely on color alone: court surfaces and paint schemes vary. Follow the lines that define the court for the format you’re playing. If you’re unsure, ask before the match rather than trying to settle it during a close point.
There is also a net detail worth knowing. On a court set up for doubles, the net posts sit outside the doubles sidelines. For singles on that same setup, singles sticks support the net at points three feet (0.914 m) outside the singles sidelines. That keeps the net at the proper height over the narrower singles court. These supports don’t change where a ball is in or out, but they explain why the net hardware may look different between formats.
Common boundary mix-ups
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“The alley is always out.” No. It is out in singles, and in for doubles rallies.
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“Doubles serves can land in the alley.” Not on the first bounce. The serve must land in the correct service box, whose side boundary is the singles sideline.
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“A ball touching a line is out.” The reverse: a ball touching the relevant boundary line is in.
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“If I’m standing in the alley, that makes it part of the court.” Player position does not define the boundary. The format and the ball’s landing spot do.
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“The service court gets wider in doubles.” It doesn’t. The service boxes are the same in singles and doubles.
For an informal match, it helps to agree that players will call their own lines clearly and promptly, especially when the ball lands near the inner singles sideline or outer doubles sideline. If you’re playing under formal rules, the relevant court lines and officiating procedures determine the call. Either way, a quick, confident call is fairer than waiting to see whether your opponent objects.
Frequently Asked Questions
Are doubles alleys in during the serve?
No. A serve must land in the correct diagonal service box, which ends at the inner singles sideline. A first bounce in the alley is a fault. The alleys become part of play after a valid serve has landed.
Can you hit a doubles alley shot in singles?
You can hit toward it, but the ball must land inside the singles sidelines. If it lands in the alley, it is out in singles, even though that same landing spot would be in during a doubles rally.
Are the service boxes different in singles and doubles?
No. The court is wider for doubles rallies, but the service boxes are the same size in both formats. The singles sideline remains the side boundary of each service box.
Is a ball on the sideline considered in?
Yes, if it touches the line that forms the boundary for that shot. For a singles rally, that means the inner sideline. For a doubles rally, it means the outer doubles sideline. A serve must touch or land inside the correct service-box boundaries.
Final Thoughts
Keep one simple rule in mind: singles uses the inner sidelines, while doubles rallies use the outer sidelines. The alleys are out for singles and out for the first bounce of a serve in either format—but they’re in for doubles once the rally is underway. Remember that split, and the court’s extra stripes stop looking like a puzzle. They become what they’re meant to be: clear boundaries and, in doubles, a whole extra lane of tactical possibility.
