Crop or fit
Crop keeps only the part inside the frame. Drag the frame to move it, drag a corner or an edge to resize it, or use the arrow keys (Alt with the arrows changes the size). With a fixed ratio the frame keeps its shape. Use the Preview frame slider to look at other moments of the video, so a person who moves around stays inside the frame the whole time.
Fit with background keeps the whole picture and places it in the middle of the new shape. The empty space is filled with a blurred, enlarged copy of the video itself, which is the look you often see when a landscape video is posted as a vertical story, or with plain black, white or a color you pick.
Which ratio for which place
9:16 is the vertical full screen format of Reels, Shorts, TikTok and stories. 1:1 is a square that works in almost every feed. 4:5 is a tall portrait that takes up the most room in Instagram and Facebook feeds. 16:9 is the normal widescreen of YouTube, televisions and laptops, and 4:3 suits older cameras and presentations. Free lets you crop any shape, for example to remove black bars or a watermark at the edge.
The size of the result is shown under the preview. When cropping, it is the size of the frame in pixels; when fitting, the long side keeps the long side of the original, so a 1920×1080 video fitted to 9:16 becomes 1080×1920.
Quality and formats
Cropping changes every frame, so the picture is encoded again at high quality: H.264 in MP4 and MOV, VP9 in WebM and MKV. The sound is copied unchanged, or converted to AAC when an MP4 or MOV file needs it. The result keeps the format of the original. Everything runs on your device, so a long 4K video can take a few minutes on a slower computer.