Smaller videos, still sharp
Phones record at high bit rates, so a two minute 4K clip can easily reach several hundred megabytes. Most of that is not needed to watch it on a screen. The compressor re-encodes the video with a bit rate based on its resolution and, if you like, scales it down: 720p is plenty for WhatsApp, Telegram and email, 1080p for YouTube and presentations.
Encoding uses the hardware encoder of your device, so even long videos are compressed quickly, and the result is always an MP4 with H.264 video and AAC audio.
Private by design
The video never leaves your device, which matters for family videos, interviews and confidential recordings. If the compressed file would not be smaller, you get the original back.