Trim video
In your browser, no upload
MP4
cut on a keyframe · not re-encoded
Video
MP4 · MOV · M4V → MP4Specification
7 rows| Item | Value | Notes |
|---|---|---|
| Input | MP4, MOV, M4V | Read from the file itself, not its name |
| Output | MP4 | The same picture and sound in a new container |
| Cut point | The keyframe before it | The result says how far back that was |
| Quality | Untouched | No frame is decoded or encoded |
| Sound | Kept | The sound track is copied too |
| File size | No limit | Only the file’s index is read; the picture stays on disk |
| Processed in | This browser | Not sent to a server |
What happens
4What happens, and why
Choose a start and an end and the piece between them becomes a new MP4. Nothing is decoded: the frames in the result are the source file’s own bytes, in the order they were already in, with a new index written around them. That is why it finishes in a second rather than a minute, and why the badge says the file was not re-encoded.
A video does not store every frame whole. A keyframe is a complete picture; the frames after it hold only what changed since, so they cannot be shown without the ones before them. A cut can therefore only begin at a keyframe. This page moves the start back to the keyframe before the moment you asked for — never forward, which would quietly drop part of what you asked to keep — and says how far it moved. It is the same bargain as cropping a JPEG on its block grid: the result is exact, the origin snaps.
Keyframes are usually one or two seconds apart and the recorder decides where they go, so how far the start moves depends on the file rather than on this page. Landing on a chosen frame instead would mean rebuilding every frame between the keyframe and it, which is a re-encode and a loss of quality. This page does not do that. It tells you where the cut really is.
The file is never uploaded, and it is never held in memory either: only the index at the end of it is read, so a two-hour recording opens as fast as a ten-second one, and the piece you download is assembled from the parts of the file already on your disk. A range shorter than 0.2 seconds is refused.
FAQ
4Why did my start time move
Because the frame you picked is stored as the difference from the frames before it, and a player cannot begin there. The cut moves back to the last keyframe at or before your start. The line under the result says how many seconds that was.
Can it cut exactly where I want
Not without re-encoding, which this page does not do. A cut that starts on any chosen frame has to rebuild the frames between the keyframe and it, and rebuilt frames are a new generation of loss. The honest options are a cut that snaps and keeps the original quality, which is this page, or an editor that re-encodes.
Does it work with a MOV from a phone
Yes. A MOV is the same format under a different name, and the result comes out as an MP4. The display matrix a phone writes its rotation into is carried over, so a portrait clip stays portrait.
Is the video uploaded
No. The browser reads the file from your disk and writes the new one on this page. There is no upload endpoint on this site, so there is nowhere for the file to go.