Most recordings run longer than the moment worth keeping: a phone clip that opens with ten seconds of fumbling, or a screen recording with the setup at the beginning. Trimming removes the unwanted head and tail so the file is shorter, lighter and ready to send.
This trimmer runs in your browser. Load one MP4, MOV, WebM, MKV or AVI file, mark where the clip should start and end, choose between a fast cut and a precise cut, and download the result. The trimmed file keeps the container of the original and gets -trimmed added to its name, so the source video is never overwritten.
Why there are two ways to cut a video
Compressed video does not store every frame as a full picture. Every so often the encoder writes a keyframe, a complete image, and the frames in between only record what changed since the previous one. Phones and cameras commonly place a keyframe every one or two seconds; screen recorders and some streaming encoders space them much further apart. A frame in the middle of that chain cannot be shown on its own, because it depends on the frames before it.
That is why the tool offers two cut modes. Fast copies the existing compressed frames into a new file without decoding them, a technique called stream copy. It is quick and loses no quality, but the clip has to begin on a keyframe, so the start snaps back to the nearest one, which can be up to a few seconds before the point you chose. Precise decodes the selection and encodes it again, so the first frame is exactly the one you picked, at the cost of time and a small generation of compression.
When trimming is the right job
Removing dead air from phone clips
Clips of a speech, a goal or a pet trick usually have a slow start and an end where the phone is lowered. Fast mode trims both and leaves the picture exactly as recorded.
Getting under a size or length limit
Messaging apps, email and upload forms often cap file size or duration. Cutting a recording down to the relevant minute is usually the simplest way to fit.
Cutting a clean excerpt for a presentation or tutorial
When a clip must start on a precise frame, such as the instant a slide changes or a button is clicked in a screen recording, use Precise so the excerpt opens exactly there instead of a second or two earlier.
What happens on your device
The cutting is done by ffmpeg compiled to WebAssembly, running inside the browser tab. This converter is about 31 MB and downloads the first time you use it; after that your browser keeps a copy. It runs on a single thread, so Fast cuts are quick, while Precise cuts of long or high-resolution footage take far longer than in desktop software that can use every processor core and the graphics chip.
A Precise cut is re-encoded in the original container: MP4, MOV and MKV clips become H.264 video with AAC sound at 128 kbps, WebM clips become VP8 with Vorbis audio, and AVI clips use MPEG-4 Part 2 with MP3 sound. If a file cannot be stream copied, a Fast cut falls back to re-encoding automatically and says so. Files can be up to 500 MB; anything above 200 MB may exhaust the memory a phone or some browsers allow.
How to use this tool
- Drop a video on the box above or click Choose a file. MP4, MOV, WebM, MKV and AVI are accepted.
- Drag the two handles on the timeline, type times such as 1:05.5 in Start and End, or pause the player where you want and press Set start here or Set end here (the crosshair buttons).
- Press Play selection to check the clip, then pick Fast or Precise under Cut mode.
- Press Trim video, preview the result and press the download button.
Limitations
- One file and one continuous section per run. To remove a middle part, trim twice and join the pieces in a video editor.
- Precise mode is slower and can cost a little quality, because it re-encodes.
- Browsers often cannot preview MKV and AVI files. They are still trimmed, but you set the times by typing or dragging rather than by watching.
- Files larger than 500 MB are not accepted, and very long or 4K clips can run out of memory on phones.