Video Trimmer — Free, in Your Browser

Yes, with libx264. ffmpeg can do a stream copy (no re-encoding) on the keyframe boundaries, but for arbitrary start/end times within a GOP (group of pictures), re-encoding is required. We use `-preset ultrafast` to keep the re-encoding fast — visual quality is preserved at the default CRF 23.

The re-encode still works — ffmpeg's libx264 picks the right keyframe placement. The result is a clean clip with no glitches at the boundary. There may be a half-second of 'ramp up' at the very start of the trimmed clip if ffmpeg has to start a new GOP, but for a 23 CRF output it is usually imperceptible.

Trimming is the right call for any of these: Screen recording with extra at the start or end. Every screen recorder captures a few extra seconds while you fumble to stop. A 3-minute recording with 15 seconds of fumbling at the start is a 2:45 trim. Cutting a specific segment for a quote. 'I want the part from 4:12 to 4:30' is a trim, not an edit. Trimming preserves the audio, the framing, the quality — just takes the slice you want. Removing dead air at the start. A 90-second recording that has 20 seconds of 'OK so...' before the actual content. Trim the start to the actual content. Shortening a long demo for a chat. A 4-minute demo clipped to 30 seconds for a Slack message. The chat-friendly length is what gets watched.

We use ffmpeg.wasm 0.12. The trim command is: ``` ffmpeg -ss -i input.mp4 -t -c:v libx264 -preset ultrafast -crf 23 -c:a aac -b:a 128k -movflags +faststart -y trimmed.mp4 ``` The `-ss` flag sets the seek time, `-t` sets the duration. Both flags are placed before the input file for fast seek (keyframe-aligned) and after for accurate seek (frame-accurate). We use fast-seek (before input) since the user picked the range with a slider, not frame-accurate.

We do not upload your video to any server. Trimming happens entirely in your browser via ffmpeg.wasm. Your video never leaves your device. The output clip is a Blob URL pointing at in-memory data. The only network traffic is the initial 31 MB ffmpeg.wasm download (cached for the rest of the session).

Not in this tool — one trim per pass. If you need to extract two or three non-contiguous segments, run the trimmer twice and concatenate the results in any video editor (or use a future Pullsy multi-segment tool).

Yes. ffmpeg re-encodes the audio alongside the video (AAC at 128 kbps), keeping the original timestamps. There is no drift over the trimmed range.

Any video format that ffmpeg can read: MP4, MOV, WebM, MKV, AVI, FLV, M4V, 3GP, TS. The output is always MP4 (H.264 + AAC) for compatibility.