Answer: Popcorn is not very keto-friendly, as it's very high in carbs.
As much as we all love popcorn, it's too high in carbs to fit the keto way of eating.
A 3-cup serving of popcorn contains 15 g net carbs, so you'll need to pick a different movie snack. Try a low carb nut, such as pecans or brazil nuts. If you want the puffed texture of popcorn without the carbs, consider pork rinds.