BrowserTools

Video Trimmer

Cut video clips by start and end time

By Guga — BrowserTools maintainer, Tbilisi, Georgia Updated 2026-08-12
Free Private No uploads

Fast mode still needs the engine: about 30 MB of WebAssembly FFmpeg comes from unpkg.com on your first run here and is cached by the browser afterwards. Nothing about your video is sent anywhere.

What is Video Trimmer?

Two numbers and a mode. In Fast mode the video and audio streams are copied rather than re-encoded, so a two-minute clip takes about a second and quality is bit-for-bit unchanged — the cost is that the cut lands on the nearest keyframe, which with a typical two-second GOP can drift up to a couple of seconds from what you typed. Precise mode re-encodes with H.264 at CRF 23 and AAC audio so the boundaries land on real frames, and the trade is time proportional to clip length. Either way the output is MP4 with the same base filename. If your source is a MOV, MKV or WebM, prefer Precise: Fast mode copies whatever was inside, and a stream that does not belong in an MP4 container can produce a file some players refuse.

Trim the start and end of a video without re-encoding when possible, keeping quality lossless and processing instant. Runs locally with FFmpeg WebAssembly.

Private Video Trimmer In Your Browser

Video Trimmer is processed locally with client-side JavaScript. Your files never touch a server, and there is no queue to wait in.

Step-by-Step

How to use Video Trimmer

1

Drop the source video onto the panel, then enter a Start and End time in seconds using the 0.1 step controls.

2

Choose a mode from the dropdown: Fast (lossless) for a quick cut, or Precise (re-encode) when frame accuracy matters.

3

Press Trim video. The first run downloads the engine; subsequent ones begin immediately.

4

Compare the Original and Result sizes — a Fast trim barely changes them, a Precise trim usually shrinks the file — then download the MP4.

Key Capabilities
  • Offers a lossless stream-copy mode alongside a frame-accurate re-encode mode from the same two fields.
  • Treats the end time as a floor of half a second past the start, so the field pair cannot produce a zero-length clip.
  • Always emits MP4 with H.264 video and AAC audio in Precise mode, regardless of the source container.
  • Displays the source and trimmed file sizes together, making the effect of re-encoding immediately visible.
Common Use Cases
  • A video editor clipping the first eight seconds off a screen recording where the app was still launching.
  • A teacher trimming a 50-minute lecture down to the three-minute answer that matches a quiz question.
  • A developer isolating a 12-second reproduction of a UI bug from a longer debugging capture.
Clear Answers

Frequently Asked Questions

Why did my cut start at the wrong place in Fast mode?
Because Fast mode copies streams rather than re-encoding, and MP4 and WebM only store a full picture at keyframes. A file written with a two-second keyframe interval can only cut on those boundaries, so your requested 10.0 might arrive at 9.1 or 11.4. Switch to Precise mode and the boundary will be exact.
Why is Precise mode so much slower?
Copying a stream is a memcpy; producing an H.264 stream means decoding every frame, filtering it and encoding it again. That work is CPU-bound, so a ten-minute Precise trim is a genuine multi-minute job while the same clip in Fast mode returns almost immediately.
Can I trim a MOV or MKV safely?
Use Precise mode. It re-encodes to H.264 and AAC and writes a standard MP4, so the container question disappears. Fast mode copies the original codecs into an MP4 wrapper, which is fine for an H.264 source but can leave a file that some players will not open.
Does Fast mode touch my quality at all?
Not one bit of the picture or the samples. The containers are rearranged around untouched packets, so the result is the same encode at a smaller size, plus whatever the keyframe snap included. The first run still costs a roughly 30 MB engine download from unpkg.com, cached afterwards.