Video Editor

Grab one section out of a longer video without uploading it anywhere. This trimmer runs ffmpeg.wasm — a WebAssembly build of ffmpeg — inside your browser, so a private recording, a raw screen capture, or a downloaded clip never leaves your device. It's the right tool when you want the first 20 seconds or that one 5-second moment and nothing else.

Steps

1. Choose a video. Any file your browser accepts as video/*.
2. Set the start (seconds) and duration (seconds) of the part to keep. Both accept decimals in 0.5 steps — start defaults to 0, duration to 5, and the minimum duration is 0.1 seconds.
3. Trim & download. On desktop you get an MP4 file; on a phone the share sheet opens so you can save it to your gallery.

The first run downloads the ffmpeg engine once (a few MB of WebAssembly). After that it's cached, and subsequent trims skip straight to processing.

Why it's fast: stream copy, no re-encode

The trim copies the existing video and audio streams straight into the output instead of decoding and re-encoding them (-c copy under the hood). Nothing is recompressed, so there's zero quality loss and the operation finishes in a fraction of the time a re-encode would take — even a large 4K clip trims in seconds, because ffmpeg is just moving packets, not crunching pixels.

The keyframe gotcha (read this before you're surprised)

Stream copy has one honest limitation: it can only cut on keyframes. Video compression stores full frames (keyframes) only every so often — often every 1–10 seconds — and the frames between them are stored as differences. Because the tool doesn't re-encode, it can't fabricate a new keyframe at an arbitrary spot, so your cut snaps to the nearest keyframe at or before your start time. Ask to start at 7.0 seconds and, if the closest keyframe is at 6.0, the clip may begin about a second early. This is normal ffmpeg stream-copy behavior, not a bug. If you need the cut to land on an exact frame, that requires re-encoding, which this trimmer deliberately avoids to stay fast and lossless.

Output format caveat

The result is always written into an MP4 container, whatever the source was. Since the streams are copied rather than converted, the codecs inside stay as they were. For a typical H.264/AAC source that's perfect. But if your input is something MP4 doesn't naturally hold — a VP9/Opus WebM, say — copying those streams into an .mp4 can produce a file some players won't open. In that case, convert the clip first (or convert the trimmed output) with the Video Converter, which re-encodes into a clean, compatible format.

When to reach for other tools

This tool does one thing — cut by start and length. To change format, resolution, or codec, use the Video Converter. To extract just the audio, convert the clip to MP3 there. Everything here happens locally via ffmpeg.wasm, so the original video is never transmitted to a server.