Two ways to cut a video
Compressed video does not store every frame as a full picture. It stores a complete picture, called a keyframe, every second or few seconds, and for the frames in between it only records what changed. That design is what makes video files small, and it is why there are two ways to trim.
Lossless cut (fast). The tool copies the original compressed data between your start and end points straight into a new file. Nothing is decoded or re-encoded, so a cut from an hour-long recording takes seconds and the picture is bit-for-bit identical to the original. The catch: the clip must begin on a keyframe, because the frames after it depend on it. So the start moves back to the nearest keyframe before the time you chose.
Precise cut (re-encode). The tool decodes the frames you selected and encodes them again at high quality, so the clip starts and ends on exactly the frame you picked. This takes longer, because every frame is processed, and it loses a very small amount of detail.
Before you cut, the tool looks up the keyframe and tells you exactly where a lossless cut would begin.
Worked example
You have a 5-minute screen recording and want the part from 1:13.00 to 1:45.00.
- The recorder stored a keyframe every 2 seconds, and the one before 1:13.00 is at 1:12.00.
- Lossless: the clip runs from 1:12.00 to about 1:45.00, so it is 33 seconds long with one extra second at the start. It is ready almost instantly.
- Precise: the clip runs from exactly 1:13.00 to 1:45.00, 32 seconds. At 30 frames per second that is 960 frames to re-encode, which a laptop typically handles in well under a minute.
| Lossless | Precise | |
|---|---|---|
| Speed | Seconds, even for long videos | Depends on clip length and device |
| Quality | Identical to the original | High, with a tiny generation loss |
| Start point | Previous keyframe | Exact frame |
| Best for | Long recordings, rough cuts, archives | Short clips, social posts, exact timing |
How far apart keyframes are depends on the source. Phone cameras usually place one every 1–2 seconds; screen recorders and streams can space them further apart.
How to pick the exact spot
- Drag the handles across the thumbnail strip to get close.
- Play the video and press Start at or End at when you reach the moment you want.
- Type a time in the Start and End boxes. You can write 75.5, 1:15.5 or 1m15s.
The preview jumps to whichever handle you moved last, so you can see the first and last frame of your clip before cutting.
Tips and edge cases
- Shorter is smaller. Trimming is the easiest way to cut file size. To shrink it further, run the clip through the Video Compressor.
- Make it loop. A few seconds of video can become a GIF with Video to GIF.
- Keep the sound only. After cutting, use MP4 to MP3 to save the audio, or cut an audio file directly with the Audio Trimmer.
- Format is kept. MP4 stays MP4, MOV stays MOV, WebM stays WebM and MKV stays MKV. Other formats are saved as MP4. To switch format, use the Video Converter.
- Unplayable formats. If your browser cannot play the file directly (some MKV files), the preview shows decoded frames instead of a player.
- Huge files. The finished clip is held in memory until you download it. For clips over about 2 GB, use a computer with plenty of free memory.
Privacy and browser support
The video stays on your device: it is read from your disk in pieces and processed by your browser’s built-in WebCodecs engine. Trimming works in Chrome, Edge and Opera 94 or newer, Firefox 130 or newer on a computer, and Safari 16.4 or newer.