Trimming by stream copy
There are two ways to shorten a video. You can decode every frame, throw away the ones outside your range, and encode what is left — slow, and lossy. Or you can copy the compressed packets straight across and simply not copy the ones you do not want.
This tool does the second. Nothing is decoded, nothing is re-encoded, and the bytes inside your clip are identical to the bytes in the source. On a large file that is the difference between waiting seconds and waiting many minutes.
Keyframes, and why the cut is approximate
Video codecs do not store every frame in full. A keyframe is a complete picture; the frames after it are stored as differences from what came before, which is what makes video compression work at all. Keyframes typically appear every two to ten seconds.
A stream copy has to begin at a keyframe. Starting mid-sequence would hand the decoder a set of differences with nothing to apply them to, producing a burst of visual garbage until the next keyframe arrived. So the cut point moves back to the nearest keyframe at or before where you put the handle.
In practice this means your clip may include a little extra footage at the start. If you need the cut on an exact frame, the only route is a re-encode — which costs both time and a generation of quality, and is why this tool does not do it by default.
Choosing your range
The preview seeks as you drag either handle, so you can see the frame you are cutting at rather than reasoning about timestamps. Because the start may drift back to a keyframe, it is worth leaving a little slack rather than trying to land precisely on the first frame you want.
Common uses
- Pulling a short clip out of a long recording to share
- Cutting dead air off the start and end of a screen recording
- Extracting one moment from a phone video without an editing app
- Shortening a file to get it under a messaging or upload size limit
Why doing this locally matters
Video files are large and frequently personal. Uploading a 500MB recording to an online trimmer means a long wait, a copy of your footage on infrastructure you do not control, and a service that has every incentive to keep it. Doing the work in the browser removes all three problems at once.