Video Trimmer

What it's for

Cut a video down to the part you need before you send or post it, without installing an editor or uploading it. MP4 and MOV files (phones, cameras, most screen recorders) are cut by copying the frames you keep into a new file, so it takes moments even for a long video, and the picture and sound stay exactly as they were.

For example, when a phone video of a talk is 20 minutes long and you only need one answer, play to where it starts, press Start here, play to where it ends, press End here, and save.

How to use it

Choose a video or drop it on the page. Play it and use Start here and End here to take the times from the player, or type them in seconds. Untick Keep the sound to save it silent (remembered in this browser).

Save the trimmed video saves <name>-trimmed.mp4 (or .mov). The message gives the times it covers and its size. Compressed video can only start cleanly on a key frame (a full picture, usually every second or two), so the cut starts at the key frame at or just before your start time, and the message says so when that’s earlier.

A WebM, MKV or other video the browser plays is played through and recorded again: that takes as long as the clip, and the result is a WebM (or MP4 in browsers that record it).

Example

In the Screen Recorder, record about 10 seconds as MP4, save it, and open it here. Set Start to 2 and End to 5, and Save the trimmed video.

The message reads like Saved screen-recording-…-trimmed.mp4: 2.00 s to 5.00 s, … not re-encoded., perhaps with a note that it starts at an earlier key frame. The saved video plays for about 3 seconds.

Good to know

An MP4 or MOV cut can start up to a few seconds early because of key frames. Videos recorded again (WebM and others) lose some quality, need the page kept in front while they record, and take as long as the clip.

The video never leaves your computer; MP4 and MOV files are read in pieces, so large ones don’t need to fit in memory.