Video Trimmer

Why a video won't cut exactly where you clicked

Video isn't stored frame by frame. It's stored as occasional complete frames — keyframes, or I-frames — and, between them, instructions describing what changed. That's what makes video files small enough to exist: a talking head only needs the lips redrawn.

The consequence is that a cut can only start at a keyframe. Ask to cut at 0:07 and if the nearest keyframe is at 0:06, the clip either starts a second early or the first second has to be rebuilt from scratch. Keyframes are typically two to ten seconds apart, which is why 'trim' in a browser is rarely frame-accurate — and why a tool that promises otherwise is quietly re-encoding your whole video.

The two ways to trim, and their prices

• Cut on keyframes — instant, lossless, and your cut point moves to the nearest keyframe. Right for almost everything: sending a clip, cutting dead air off the end, extracting a section of a recording.
• Re-encode — cuts exactly where you asked, takes as long as the video is, and loses a generation of quality. Right when the frame matters: a beat, a punchline, a proof.
• The choice is almost always the first one. A second of slack at the start of a clip nobody will notice; a re-encode of a 4K screen recording will heat your laptop for ten minutes and look slightly worse.

Working within what a browser can do

Video processing in a tab is real but bounded. The file has to fit in memory, which puts a practical ceiling somewhere around a few hundred megabytes depending on your machine — a phone will manage less than a desktop. Long 4K recordings are where you'll feel it first.

If the file is too large, trim it into pieces rather than all at once, or use Video Compressor to bring the size down first. If you only want the audio, Audio Extract skips the video entirely and is far faster.

Nothing uploads, and that changes what you can trim

The everyday reason to trim a video is to send it — and the everyday problem with online trimmers is that sending it to them is the thing you were trying to avoid. Screen recordings show your desktop. Meeting recordings have people in them who didn't consent to a third-party website.

This runs on your machine. The file is read from disk into the tab and never leaves it, so a recording of a private call stays a recording of a private call.