Are you taught to snap or freeze the foot in mawashi geri?

[Prototype]

I get mixed instructions. A black belt told me to NOT snap the kicking foot, and instead have it static when the kick has been lashed out, and then retract the entire foot. My instructor however tells me to snap the foot in the air and retract it.

Which one is the formally correct way, or are both formally correct?

[sensei8]

If it was me, I'd follow the instructions of my Sensei, and not any black belt; methodologies separate styles quickly. How one style executes a technique is not universal across the board.

[Wastelander]

Well, as sensei8 suggests, I would do what your instructor says. That said, I'm also not entirely sure I understand what you're describing. Even so, your chief instructor is the one who sets the standards for your school

[Wado Heretic]

I would follow Sensei8's advice; go with the person who is in charge.

With that said; I have never found a "traditional" round kick method in karate. After-all; it evolved for competition, or was adopted from Muay Thai, depending on the system. There are many ways to perform a roundhouse, and none are necessarily "wrong", although there are some which are objectively worse when compared to other methods.

Personally; I would fix the foot, just because it is safer in a full-contact context, but I tend to aim with the shin, compared to the foot as used a lot in Sport Karate circles. One can snap the foot, and do so safely, and having the foot relaxed can help with speed; but it's very dangerous if you connect and get the timing wrong.

So, I understand the black-belts advice; he isn't necessarily wrong, even if he is advising differently to the head instructor. In this case; I would argue going with your instructors advice, because you are his student, or experimenting and seeing what gets the best results for you.

[Alan Armstrong]

When kickng in the air snapping the kick back will prevent you from spinning, as opposed to a fully committed kick that will spin you due to the momentum.

You will have a variety of kicking options to choose from in the future, try to understand why you should and shouldn't do what you are doing.

A Muay Thai kick in a karate kata isn't appropriate but while in kumite it might be very effective.

When in doubt always ask your sensei, things take time to sink in, always refer back to your sensei at a later time if need be.

Ask three people the same question, chances are you will get three different answers, then become confused; better to ask one expert your sensei, accept the answer given and move along.