Ever since the release of IT Chapter Two, people are ecstatic and excited to watch what happens after the conclusion of the first movie. 

Some people have watched Chapter Two, skipping the first movie entirely. This is not recommended. There are a multitude of reasons to not skip the first movie of the franchise.  

One reason to not skip the entirety of the first movie, is because Pennywise’s actions and origin to the conflict is lost.  The cast in the first movie reunite to find a way to stop the mad clown from terrorizing and killing everyone in town, and by skipping the first part of the film, the impact of the full story line will be lost.

You also skip character development in the movie.  Over the course of two films, many characters have changed personalities and relationships that began in chapter one that translates into chapter two.

Overall, if you are planning to watch IT Chapter two, you should plan to watch the first one before doing so.