How to letterbox a short video
1. Drop one video you already have. Audio-only files and pictures are refused here. 2. Pick 16:9, 9:16 or 1:1. 3. Leave the bars black, or switch them to white. 4. Press “Add bars” and download the MP4.
A 4:3 clip going into 16:9 gets bars on the left and the right. A wide clip going into 9:16 or a square gets bars on the top and the bottom. GustKit does not scale the picture up and does not cut it. The frame grows until the shape matches, with even pixel sizes so the MP4 can play. Keep the original until the bars sit where you expect.
Bars keep the picture, crop throws part of it away
Crop video cuts the frame down to a shape. This page keeps every pixel and fills the gap. Pad image does the same job for a photo, on the canvas. Resize video changes the pixel size of the picture itself. Change video FPS changes how many frames are stored and leaves the shape alone.
The clip stays in this tab
The first visit downloads FFmpeg. Later visits reuse the browser cache. Clips longer than the limit on the page are refused, because every frame is re-encoded here. GustKit does not fetch video from a link.
How to check the bars before you replace the clip
1. Play the download and pause on a face or a logo. It should still be fully visible. 2. If the bars ate the wrong side, switch the shape and run again. 16:9 grows the sides of a tall clip. 9:16 grows the top and bottom of a wide clip. 3. Keep the original until the soundtrack still lines up.
Crop video is the page that cuts pixels away. This page only adds bars. A long clip is refused because every frame is re-encoded. Trim video is how you get under the limit. Nothing is uploaded.