Trim a Video
Pick a video, set a start time and duration — it's trimmed in your browser, nothing is uploaded.
About this tool
Cut a clip out of a video without leaving your browser. Pick a video, set a start time and a duration (both in seconds), and you get just that window back — the file never leaves your device.
How it works
The tool runs ffmpeg, compiled to WebAssembly, with a stream-copy trim
(-c copy): it seeks to the start time, keeps duration seconds, and writes
the result in the same container as your input (an mp4 stays mp4, a webm
stays webm) — without re-encoding. That makes it fast and lossless: the
original video and audio streams are copied through untouched.
Notes
- Lossless — no re-encode. The streams are copied byte-for-byte, so there's no quality loss and it's fast. Because the output keeps your input's container (mp4 → mp4, webm → webm, mov → mov, mkv → mkv), the copy is always valid — there's no codec conversion to fail on.
- Keyframe seeking. The start time snaps to the nearest preceding keyframe, so the cut may begin slightly before the exact second you asked for. This is the trade-off for a fast, lossless copy.
- Private by design. Everything runs in your browser. No upload, no server.
- Works offline once the page has loaded.
FAQ
Why doesn't my clip start at the exact second I typed?
The trim seeks before decoding (-ss ahead of -i) and copies the streams
without re-encoding, so playback can only begin at a keyframe. The cut snaps to
the nearest keyframe before your start time — a small drift is normal and is
the price of a fast, lossless trim. Frame-exact cutting would require
re-encoding the video.
The trim failed with a codec error — what's wrong?
The output keeps your input's container, so a stream copy is normally always valid — an mp4 stays mp4, a webm stays webm, and their streams copy through untouched. A codec error only shows up for an unusual container the tool can't keep: it falls back to mp4, and streams that aren't mp4-compatible can't be copied into it. In that case re-encode or compress the clip first (the video-compress tool), then trim the result.
Does trimming reduce the video quality?
No. Stream-copy passes the original video and audio bytes through untouched — only the container timestamps change. What you can't do is pick a fractional window smaller than the keyframe spacing, and the duration must be greater than 0 seconds.
Is my video uploaded anywhere while it's being trimmed?
No — ffmpeg runs as WebAssembly inside the page, so the file is read and cut entirely on your device, and the page even keeps working offline once loaded.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool video-trim 'url=https://example.com/input' 'start=0' 'duration=5'New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/video-trim/?url=https://example.com/input&start=0&duration=5Machine-readable descriptor: tool.json — title + parameters JSON Schema for agents.