How to compress videos with Quicktime Player Here's how you use Quicktime to compress your video files: Open Quicktime Player. A popup should appear asking you to select your video. If it doesn't, click File > Open File. Then, click File > Export As… You'll see a list of video resolutions. Choose the next lowest resolution. Name your video and choose a location to save it. Also, To Secure your macOS from virus and trojans, use always a mac optimization software like Mac optimizer .