Apple’s default media player actually includes a number of great options for making your videos smaller. The only drawback to it is that you can't use it on any other operating systems.
To make a video smaller with QuickTime, open the app from your Applications folder and click File > Open File to load your video.
To begin making your video smaller, click File > Export As. Unfortunately, QuickTime doesn't give you as many options as some other apps. You’ll see 4k (if applicable), 1080p, 720p, and 480p options.
There are many affordable applications to enable you to compress various video files and reduce video file size. Here are a few we suggest: