Those tail wags are all about communication, both with humans and other canines.
illustration of dog wagging his tail
Credit: Yeji Kim

Whether your dog has a sweeping side-to-side tail wag or a high-speed wiggle butt, it always makes you feel good, right? But does it mean he's happy?

A dog's tail can tell you a lot about how he's feeling. While a person uses facial expressions to convey her emotions, a dog primarily uses his tail and other body language.

That's where the age-old question comes in: What does it mean when a dog wags his tail?

"This is a great question because many people think that dogs who wag their tails are happy, but that's not always the case," says Lauren Novack, ABDBC, KPA-CTP, FPPE, and behavior consultant at Behavior Vets in New York City. "A tail's position and movement are only a part of the whole picture. If a dog's whole body is a sentence, their tail is one word in that sentence," she explains.

How to Decipher What It Means When a Dog Wags Their Tail

When attempting to interpret the wag, there are three main things to look at: 

  1. Body stiffness
  2. Tail position
  3. Tail movement

First, notice if the dog's body is stiff. If it is, this likely means he is anxious and not inviting interaction, so keep your distance. A relaxed body is more likely to indicate your dog is open to interacting. 

Next is the tail position. A neutral, relaxed tail typically lies flat, somewhere between a tucked tail and a tail that's held high. Knowing where your pup's tail naturally sits when he's relaxed can help you understand his communication when he's happy—or upset.

Lastly, look at the tail movement and speed. The speed at which a dog wags his tail indicates the level of arousal, which can mean stress or eustress (a positive form of stress). In other words, the faster the tail wag, the more emotion he's trying to convey. A slower wag may indicate anxiety and insecurity while a high-speed tail could mean excitement or extreme fear.

To make matters more complicated, Novack adds that not all tails look the same, so "tucked" and "raised" may not look the exact same on two different dogs. Things may look a little different on dogs with naturally curled or kinked tails. Pay attention to your dog's tail during different moods so you know what's normal for him. Luckily, the tail movements and other body language clues are generally universal for all dogs.

Here's how to tell the meaning behind your dog's wagging tail:

Happy Wagging

"If the tail is in line with the dog's spine and parallel to the floor, they are most likely relaxed," Novack says. A relaxed pup's tail may not have much wag to it, but it won't be stiff or straight out.

When your dog feels happy, he'll typically wag his tail in a wide, sweeping motion at a neutral or slightly upright position. Your dog's tail doesn't need to be moving fast to show a positive emotion; dogs who are feeling happy will wag their tails at a moderate speed.

For good measure, watch these happy tails in action!

One tail wag that means your dog is happy is the helicopter tail. If your pup's tail is moving round and round super fast (probably alongside some adorable butt wiggles and a dopey smile), you can be certain she's feeling good.

Fearful Wagging

Sometimes a dog may wag his tail in between his legs, but just because his tail is moving doesn't mean he's happy. "When a dog's tail is tucked towards the belly, the dog is fearful," Novack says. This behavior may also be paired with a crouched body, flattened ears, and avoidant eye contact. 

If a tucked tail means a dog is fearful, then a high tail must mean he's happy, right? Not exactly.

"If the tail is held high, they are in a state of arousal that can indicate fear, anxiety, or potential aggression," Novack says. Alongside a high-held tail, a stiff body, flattened ears, staring, and growling are tell-tale signs of an upset and aggressive dog. While their tail doesn't need to be wagging to show their discontent, it's still important to notice; the faster their tail wags, the more upset they are. If a dog is showing signs of fear, it's best to let them calm down alone as they may bite if they're approached.

Curious Tails

If your pup runs into a new smell, noise, or object and isn't quite sure how to feel, his tail may be a sign of canine curiosity. A dog's curious tail will be held straight behind him and may have a slight wag, but it's more likely to be held still. Check out how this dog's tail moves straight out as she becomes inquisitive, then straight up once upset:

Typically, a curious dog will be alert—but not completely stiff. Perked up ears, sniffing, or barking are also signs of an investigative pooch. 

What Does It Mean When a Dog Wags Their Tail in Their Sleep?

If you've ever sat near a snoozing pooch, you may have noticed his tail start to wag—even while his eyes stay shut. Well, they may just be dreaming. 

Just like humans, dogs sometimes dream when they're in rapid eye movement (REM) sleep, which is a deep state of rest. Puppies and senior dogs need more sleep than adult dogs, so you may notice the bedtime wagging become more common in his older years. Along with the tail wags, you may also observe twitching, soft whimpering or woofing, or running-in-the-air paws (also called paddling).  

Wouldn't you just love to know what he's dreaming about? Is it a pleasant dream? Or a nightmare? It's really anyone's guess because the current body of canine research hasn't yet cracked that code. Maybe he's chasing squirrels, playing with his friends, or traipsing through the woods. One thing's for sure, as Novack says, it's fun for dog owners to watch their furry friends be super cute when they're dreaming … tail wags and all.

A previous version of this story included reporting by Denise Caiazzo.