Every pet owner has that feeling of joy when they come back home to a dog wagging its tail when it sees you – a tiny act that warms our hearts.

However, animal experts want you to know that a wagging tail does not always mean your dog is happy.

Dogs do express emotions with their tails, explains canine behavior expert Katja Krauss, but while we humans like to think it means it's happy, instead it just means the pet is excited.

If you want to properly read what is happening, look at the height of the tail and how fast it's moving. This should give you a warning if the animal is fearful or aggressive.

As a rule of thumb, the slower and gentler the tail movements are, the less tension the dog is feeling.

Things are different if the tail is moving faster and not swinging as far. A tight, tense tail held up high means one thing: confrontation. This is even more true if the tail stops moving.

A happy dog usually wags its tail high up and with a lot of floppy movement, sometimes almost in circles, Krauss explains.

But sometimes even happy dogs can wag their tails quickly and sharply. To know your dog's mood, you need to watch its tail in other situations, for example, when you know it feels threatened by another dog.

It also helps to take the dog's nature, anatomy and the rest of its body language into account.