From a wide video to a vertical Short
A 16:9 picture placed in a 9:16 frame fills the full 1080-pixel width and about a third of the height. ToolGPT fills the rest with a blurred, enlarged copy of the same footage, so the Short looks complete instead of floating on black. If you prefer plain bars, choose black, white or a color on the card.
The result is an H.264 MP4 with AAC audio, at your video's own frame rate up to 60 fps.