Trim a video

What it's for

Perfect for getting a clip out of a longer video: the highlight of a match, a piece of a video call, the useful part of a recording, or a scene to share. The trimmed part is re-encoded to MP4 H.264 so it's precise and plays everywhere.

Tip

Use the player above to find the exact points: pause and press «⏱️ Here» to set the start and end to the right second (or tenth of a second).

Why a video cannot be cut wherever you like

A video file does not contain a whole image for every frame: it contains a complete one every so often, the keyframe, and in between only the differences from it. Cutting at an arbitrary point therefore means starting from a description of differences without having the reference image, which is why some quick cuts show the first seconds smeared or grey.

There are two routes. Cutting on the nearest keyframe, which is instant and does not touch quality but moves the point by a fraction of a second. Or re-encoding, which allows a cut on the exact frame but rebuilds the video from scratch, so it takes longer and costs a shade of quality.

Where to put the start and the end

The typical mistake is cutting too tight. In speech it is better to leave half a second before someone starts talking and as much after the last syllable: a cut hard against the word sounds abrupt even when it is technically correct, because the ear misses the breath.

For clips meant for social media the opposite applies: the first two or three seconds decide whether anyone keeps watching, so everything before the interesting moment has to go. It is the same reason videos that open with «hi everyone, so, today I'm going to talk about» lose half their viewers before the content.

What the cut carries with it

The audio is cut along with the video, and that is where the flaws are heard: if the cut lands in the middle of a word or on a note still ringing, there is a click. If the video ends with a musical tail, it is better to move the end onto a silence, not onto the perfect frame.

Two things often needed stay outside the trim: embedded subtitles, which if they are a separate track have to be resynchronised, and metadata, such as the shooting date and GPS position, which a trim usually preserves. If the video is going to be shared, those are worth checking.

Size, and why it does not fall in proportion

Cutting a video in half does not necessarily halve the file: it depends on how much the image moves in the part that remains. A static scene takes up very little, a shaky or highly detailed shot takes up a great deal, and the same duration can weigh five times as much.

If the goal is getting under a size limit for a chat or a portal, trimming alone is often not enough: you also have to reduce resolution or bitrate, which is another operation. And it is worth remembering that email attachments grow by roughly a third against the file on disk, so the margin has to be wider than it seems.

Nearby tools

To know what the file really contains there is What video is it really, to estimate size Video bitrate and size and to compress it Compress video. For audio Extract audio from video and Video loudness, for a still image Frame from video.