While HIIT workouts are certainly intense, there is no reason why you can’t do them every day if you feel up to the challenge.
Of course, it's important to listen to your body and make sure that you aren't pushing yourself too hard.
If you're feeling good there's no reason why you can't do HIIT every day.
Due to the high impact nature of most HIIT workouts you might want to alternate between high impact and low impact workouts.
By mixing things up, you’ll keep your body guessing, it will help to prevent boredom and injury.
This way you’ll be able to maintain your workout schedule more long term, and then see even better results.