Nightcrawler is useful for English practice if you can already follow natural conversations. The language mixes everyday English with a few expressions that need attention, so it works best for learners who already have a solid base. There is enough plot detail to keep learners engaged without making the whole experience confusing. With the dialogue moving at a natural rhythm, viewers should catch most of it, although a few moments may still be challenging. If your English is close to B2/C1, Nightcrawler can be useful for getting used to faster spoken English.
