Video Trimmer

Trim the start and end of an MP4, MOV, WebM or MKV video in your browser. Fast stream copy keeps full quality, or re-encode for a frame-accurate cut.

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About this tool

What is the Video Trimmer?

Load a video, drag the two handles on the timeline or stop the preview where you want the clip to start and end, and this trimmer cuts it out. The fast mode copies the original video and audio streams without decoding them, so the clip keeps exactly the quality of the original and is ready in seconds even for long files.

If you need the cut on an exact frame, switch to frame-accurate mode, which re-encodes the selection to H.264 and AAC in an MP4. The work is done by ffmpeg compiled to WebAssembly in your browser tab, so the video never leaves your device. If a file cannot be stream copied, the tool falls back to re-encoding automatically.

  • Lossless stream-copy trimming that keeps the original container
  • Frame-accurate re-encode to H.264 and AAC MP4
  • Automatic fallback when a file cannot be copied
  • Dual-handle timeline, playhead buttons and typed times
  • Optional audio removal
  • Runs in the browser: videos are never uploaded
Read the guide: How to Trim a Video Without Re-encoding (and When You Must)

How to use the Video Trimmer

  1. Drop a video on the box or try the 4-second sample.
  2. Drag the two handles under the preview, use Start at playhead and End at playhead while watching, or type the times.
  3. Keep Fast, original quality for a lossless cut, or choose Frame-accurate if the start must be exact.
  4. Turn on Remove audio if you want a silent clip.
  5. Press Trim video, check the result in the preview and download it.

Worked examples

Shorten a phone clip

Input

2 min iPhone MOV (HEVC), keep 0:12.00 to 0:47.50, fast mode

Output

MOV of about 35 s, same quality, made in seconds

Only the packets are copied, so the time is spent reading the file, not encoding.

Exact start for a tutorial

Input

Screen recording MP4, start at 1:03.20 on a mouse click, frame-accurate

Output

H.264/AAC MP4 starting on that frame

Screen recorders often place keyframes many seconds apart, so a stream copy could start well before the click.

WebM from the browser

Input

WebM recording, cut 5 s off each end, fast mode

Output

WebM with the original VP8 or VP9 and Opus streams

The container stays WebM because stream copy cannot change codecs.

Background and insight

Modern video codecs such as H.264, HEVC and VP9 store a full picture only every so often, at keyframes, and describe the frames in between as changes from their neighbours. A group of pictures (GOP) is commonly one to two seconds for camera and phone footage and can be much longer for screen recordings. A stream copy can only start a clip cleanly at a keyframe, because the frames after it depend on it.

In fast mode the trimmer runs ffmpeg with -ss before the input (which seeks quickly), -t for the length, -c copy to copy packets unchanged and -avoid_negative_ts make_zero to fix the timestamps. ffmpeg starts at the keyframe at or before your start time, so the clip can begin earlier than requested by up to one GOP. In a test with one keyframe per second, asking for 1.5 to 4 s produced a 3.1 s clip starting at 1 s. The container is kept, so a MOV stays a MOV.

Frame-accurate mode decodes from the keyframe, discards frames before your start and encodes new H.264 video at CRF 20 with the veryfast preset and 192 kbps AAC audio, then writes an MP4 with the index at the front for quick playback. It is slower, especially for 4K, and adds a small generation loss, but the first frame is exactly the one you chose.

Common use cases

  • Sharing phone videos

    Cut the fumbling start and end off a clip before sending it.

  • Screen recordings and demos

    Remove setup time at the start and the stop-recording click at the end.

  • Meeting and lecture recordings

    Keep only the part worth archiving, without re-encoding hours of video.

  • Preparing clips for editing or GIFs

    Pull a short section out of a long file before converting or compressing it.

Tips and limitations

  • If a fast cut starts too early, nudge the start later or use frame-accurate mode for that clip.
  • Fast mode keeps the original codec. If the result must play everywhere, trim first and then run it through a converter to H.264 MP4.
  • Very large files (over about 500 MB) can exhaust browser memory on phones; desktop Chrome or Edge handle them best.
  • Some containers like MKV or AVI do not preview in browsers. The trimmer reads their length with ffmpeg so you can still type times.
  • The first trim downloads the ffmpeg engine, about 32 MB, once per visit.
  • Remove audio uses no extra time in fast mode, since the audio stream is simply left out.

Frequently asked questions

How do I trim a video without losing quality?

Use the fast mode. It copies the compressed video and audio as they are, so no frame is re-encoded, and only cuts on keyframes.

Why does my trimmed video start before the time I set?

A lossless cut must start at a keyframe, and the nearest one before your start time may be a second or more earlier. Choose frame-accurate mode for an exact start.

Is my video uploaded to a server?

No. The trimmer runs ffmpeg in your browser. The only download is the engine itself from a public CDN, once per visit.

Which video formats can I trim?

MP4, MOV, M4V, WebM, MKV, AVI, MTS and other formats ffmpeg reads. Fast mode keeps the same format; frame-accurate mode always writes MP4.

How long does trimming take?

Fast mode is limited by reading the file and usually takes seconds. Re-encoding runs at a fraction of real time for HD and slower for 4K, depending on your computer.

Can I cut a section out of the middle and join the rest?

Not in one step. Trim keeps one continuous section. Trim each part you want to keep and join them in a video editor.

Is there an in-depth guide to the Video Trimmer?

Yes. “How to Trim a Video Without Re-encoding (and When You Must)” covers the background, how it works, common pitfalls and worked examples. Read the full guide.

People also search for

  • trim the beginning of an mp4 without losing quality
  • cut the end off an iphone video on a pc
  • shorten a screen recording before sharing
  • trim a large video file in the browser
  • frame accurate video cut free
  • why my trimmed video starts a second early
  • remove the first minute of a mov file
  • trim a webm or mkv video without converting

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