MP4 is a video container for MPEG-4 Part 14. MP4 container supports motion pictures, audio, and text (subtitles). It can contain videos that encoded in H.264 and H.265(HEVC). You can read the (H.264 and H.265(HEVC) comparison) article to get a good understanding of both formats. H.256 is a new format that most browsers support but handful of desktop video players can handle. PS2PDF support compressing of MP4 with H.264 and H.265 (new). The main factor that relates quality to size in mp4 compression is called Constant Rate Factor. Constant Rate Factor(CRF) is a rate control factor (quality/file size) for H.264/H.264 encoders. Lower values of CRF produce larger output sizes but has higher quality. To reduce large high-quality videos, you can use slower Preset to compress it even more.
PS2PDF MP4 Video compressor allows you to compress MP4 files without a limit. It is the fastest online free MP4 video compressor on the web. You can compress a MP4 video (.mp4) by setting Constant Rate Factor (a General Option) to ~21 and Preset to medium to get an amazing quality compressed MP4 video.
Another way to compress MP4 Video files is to resize them to a smaller size. You can use the Resize dropdown on Output Dimension section to select a Preset Resolotions such as 8k, 4K, 1080p, 720p, 480p, 360p, 240p, and other non-standard options to reduce MP4 video width and height.
Or you can set MP4 Video width and height relatively or independently. Setting relative is preferred if you want to keep the aspect ratio intact.
Most MP4 videos you take from Windows, iPhones and Androids converted to .MP4 format or .WEMB. These formats can be open using VLC Player . In fact, VLC can open almost any MP4 video format and support Linux and MacOS platforms.
The default option is to install VLC player. On Ubuntu (Debian) you can run sudo apt-get install vlc. Make sure you have X11 installed.
Quick Time cannot open .mp4 files specially if it is encoded in H.265. You will need to install VLC player to be able to view MP4 video on MacOS.