Spacey, HandBrake is a free download ap. There is a Youtube tutorial here,
There are literally dozens of free online video compressors if you search, One I have used is Freecompress. Nothing to download and install. Simply upload your video, choose your output format (,mp4, ,MOV, etc) and start. It will tell you when the converted compressed video is ready to download, Lots of these have popped up since Tik Tok and other video social media sites have emerged.