Video Crop (MP4 export)

Features

• Crop by percentage: left, top, width and height are all percentages of the frame
• Percentages work for any resolution, so the defaults never run off the edge
• Remove letterboxing, reframe widescreen to vertical, cut a sidebar out of a recording
• Output size matches the crop by default, with no extra resampling
• An output width can be set to scale the result down for a smaller file
• Export a real MP4 (H.264 + AAC), not WebM
• Audio is kept by default — cropping the picture and losing the sound would be a surprise
• Frame rate of 24, 30 or 60 fps with three quality levels
• Missing WebCodecs or a missing H.264 encoder is reported plainly, with no silent downgrade
• Everything runs locally in the browser; the video is never uploaded

How to use

1. Drop the video in
2. Adjust the four percentages to frame the part you want to keep (the middle 80% by default)
3. Adjust frame rate and quality if needed, or set a smaller output width
4. Press Start, wait for the progress bar, and download the MP4

FAQ

How do I know which percentages to use?

Look at the preview first. To remove 12% of letterboxing top and bottom, set Top to 12 and Height to 76 (100 − 12 − 12). For a vertical crop (9:16), raise Left and lower Width until the width is about 56% of the height. The result reports the actual pixel size (`1280×480 → 1280×480` and so on), so there is no mental arithmetic — try once and read it off.

Why percentages rather than pixels?

Because pixel values are fixed in the options while video sizes are not. A tool page carries one set of defaults, and what gets dropped in may be a 1920×1080 phone video or a 640×480 old clip — with pixels, a default of "left 100, width 800" simply runs off the edge of the latter. Percentages mean something at every size, and that is the only way to give a sensible default here. When you need exact pixels, read the reported size from a first run.

Is cropping the same as scaling?

No. Cropping keeps part of the picture and discards the rest (less content, resolution unchanged); scaling shrinks the whole picture (same content, lower resolution). This tool crops. If what you want is "a smaller file with everything still there", put a smaller value in Output width — that scales the cropped picture to the width you name. The two can be used together or separately.

Does the audio get cropped too?

The audio is not cropped; it is kept whole by default. Cropping the picture is a spatial operation and there is no corresponding part of an audio track — losing the sound while only the picture was cropped would be a surprising result, so the two are deliberately kept separate. To drop the audio as well, turn Keep the audio off.

Why is the exported file not smaller?

A smaller picture does not guarantee a smaller file: the bitrate here comes from a bits-per-pixel-per-frame figure, so fewer pixels means a lower bitrate — but if the original was compressed very hard, re-encoding can come out larger. To shrink it noticeably, pick the low quality, drop to 24 fps and set a smaller output width; those three act on size directly.