Trim video online, losslessly or to the exact frame
This Trim Video tool cuts unwanted seconds off the beginning and end of a clip — the fumbling before you pressed record, the long goodbye at the end, the moment the phone went back in your pocket. Open an MP4, MOV, WebM or MKV file, drag the two handles on the filmstrip or type exact times, and download the shorter video. Everything happens inside your browser with WebCodecs and the open-source Mediabunny library (MPL-2.0), so your footage is never uploaded.
There are two ways to trim. Fast mode copies the original compressed video and audio packets into a new file without decoding them, which means no quality loss at all and a result in a second or two even for long recordings. The trade-off is that the start has to land on a keyframe. Precise mode decodes and re-encodes the frames so the result starts and ends on exactly the frames you chose. The page shows you where the keyframes fall, so you can decide which matters more for each clip.
How to use the Trim Video
- Drop a video onto the box or click to choose one. The tool reads its length, resolution, frame rate, codecs and keyframes and draws a filmstrip.
- Drag the left handle to the new start and the right handle to the new end. On a phone, drag with your finger; on a computer, focus a handle and use the arrow keys to move one frame at a time (Shift + arrow moves a second).
- Or type exact times in the Start and End boxes (hh:mm:ss.ms, or simply seconds like 65.25), or press Playhead to use the current playback position.
- Choose Fast · lossless or Precise · re-encode. In fast mode, pick which keyframe the start should snap to; the green bar under the filmstrip shows exactly what will be kept.
- Press Play selection to preview, then Trim video. Check the result in the player and press Download trimmed video.
Trim Video features
Lossless keyframe trimming
Fast mode copies the original packets byte for byte into a new MP4, MOV, WebM or MKV, so picture and sound are untouched and even an hour-long file trims in seconds.
Frame-accurate option
Precise mode re-encodes only the part you keep and starts on the exact frame you picked, with the audio trimmed to the sample.
Keyframes made visible
Ticks along the top of the filmstrip mark every keyframe, and the note under the mode switch tells you which keyframes sit either side of your start.
Touch and keyboard friendly
Large handles work with a finger, and focused handles move one frame per arrow press — handy for finding the exact frame where a clip should begin.
Exact time entry
Type hh:mm:ss.ms, minutes and seconds, or plain seconds. Times snap to real frame boundaries so the numbers you see are the frames you get.
Private by design
The video is read straight from your disk with a Blob reader and processed on your device; it is never sent to a server.
Why fast trimming snaps to keyframes
Modern codecs such as H.264, H.265, VP9 and AV1 save space by storing only a few complete pictures, called keyframes or I-frames, and describing the frames in between as changes from earlier frames. A player can only start decoding at a keyframe. If a lossless trim started on an in-between frame, that frame would have nothing to build on and the first second would show grey blocks or freeze.
Fast mode therefore begins at a keyframe. With Keyframe before you keep everything you selected plus a little extra at the start; with Keyframe after you lose a little of your selection instead; Nearest picks whichever is closer. Phones usually write a keyframe every one or two seconds, while screen recordings and web exports can space them five or ten seconds apart. The end of the trim is frame-accurate unless the file uses B-frames (frames that refer to later frames), in which case it also lands on a keyframe so nothing breaks.
Fast or precise: which to choose
If a keyframe sits within half a second of where you want to start, fast mode is almost always the better choice. Use precise mode for tight edits — a punchline, a beat drop, or a clip that must be an exact length.
| Fast · lossless | Precise · re-encode | |
|---|---|---|
| Quality | Identical to the original | Very close; a small generation loss |
| Speed | Seconds, regardless of length | Roughly real time or faster, depending on the device |
| Start point | Nearest keyframe | Exact frame |
| File size | Proportional to the part kept | Depends on the quality setting |
| Needs WebCodecs encoding | No | Yes |
Tips for a clean trim
- Play the selection before exporting: the preview plays exactly the range that will be written, including any keyframe snapping.
- To remove a section from the middle rather than the ends, use the Video Cutter, which can take out several parts at once.
- To turn one long recording into several clips, the Split Video tool cuts at markers, equal parts or a fixed length.
- Trimming does not shrink the bitrate. If the file is still too big to send, run it through the Video Compressor afterwards.
Trim Video FAQ
How do I trim a video without losing quality?
Use fast mode. It copies the compressed video and audio packets without decoding them, so the trimmed file is bit-for-bit the same picture as the original. The only limit is that the start lands on a keyframe.
Why does my trimmed video start a little earlier than I set?
In fast mode with “Keyframe before”, the start moves back to the previous keyframe because playback can only begin there. Choose “Keyframe after”, or switch to precise mode to start on the exact frame.
Is this video trimmer free and private?
Yes. It is free, adds no watermark and needs no account. The video never leaves your device; the page only downloads the Mediabunny library from a public CDN.
Which formats can I trim?
MP4, MOV, M4V, WebM and MKV with H.264, H.265, VP8, VP9 or AV1 video. The trimmed file keeps the same container where possible. AVI, WMV and FLV need converting first.
Can I trim a video on my phone?
Yes. The handles are sized for fingers and the page works in Chrome on Android. Very long, high-resolution videos may exceed the memory of older phones; fast mode uses the least memory.
Does trimming change the resolution or frame rate?
No. Fast mode keeps every setting of the original. Precise mode keeps the resolution and frame timing and re-encodes at the quality you choose.