They are all effective and all work. The style doesn't matter as much as the person you learning it form and the person taking it. So pick the school with the best instructor and you'll be all set as long as you train right.

Judo is the most practical of the few in self defense. picture somone grabbing you then getting flipped on their back. alse if you get thrown to the ground you will be able to handle your self.

Karate would be in second. Some practical stuff. But a lot BS that doesn't work. If you want to train for YEARS before anyone here would actually think you know something than karate is for you. but of course there are some sane schools, and you might have one around.

Tae Kwon do is more of a sport martial art that teaches a lot of impractical stuff along with what self defense they have.

I would go with Judo. Its good for competition, and self defense.

Learning all would be okay, as long as there is a good school that teaches it.

You don't want to get mugged? Fine, stay at home, what do you expect? Go on the streets on purpose and get mugged?

@abigail: Don't recommend your place to the person that's asking the question. Your Dojo is probably a McDojo. You're like 12 and you get a second degree black belt. Do you even Front kick bro?

well karate is the well rounded one out of the 3 since judo focuses on throws and tkd focuses on kicks. but for street self defense take something muay thai, boxing or krav maga.

Which has the best teacher? Which one spars? Which drills self-defense techniques every class?

Don't be so hang up on styles and types of martial art. There is no best styles. There are only good and bad teachers of a martial art.

Tae Kwon Do really helps with self defense. It shows you to throw/block punches, how to fight, and self defense. Also, it helps you build character. Your self confidence rises when you continue training. It can help you in situations when, for example, a drunk guy grabs onto you and won't let go. You use a self defense that really helps in that kind of situation. It's going to be a lot of work, but it's worth it. You should take it.

I do tae-kwon-do and I am a 13 years old girl and A second degree black belt

I don't know where you live but if you live in Virginia then I recommend mt..kim Marshall arts even if you are in sorry ding states there are some mt..Kim studios there too

Okay so i'm thinking of learning karate, judo, and taekwondo but i know its not possible for me to learn all of those so which one's better i'm thinking judo ? But i want to learn the one that can keep me safe from this dangerous world if i'm ever alone ?