Trim Video

Trim a video online without uploading it

This tool cuts the start and the end off a video and saves the part in between as a new file. It works with MP4, MOV, WebM and MKV files, and the clip comes out in the same file type as the original. Everything happens inside your browser tab: the video is read from your device, cut there and offered as a download. There is no upload, no account and no watermark.

• Phone videos: remove the seconds of fumbling at the start and the moment you reach for the stop button at the end.
• Screen recordings: cut away the part where you open the recorder and the part where you stop it.
• Long recordings: keep only the talk, the goal or the scene you want to send, which also makes the file smaller.

Fast or Precise: what keyframes have to do with it

Video files do not store every frame as a full picture. Some frames, called keyframes, can be decoded on their own; the frames between them depend on earlier frames. MDN describes a key chunk as one that does not rely on other frames for decoding. A cut that copies the video data unchanged therefore has to begin at a keyframe, because the frames right after your start cannot be shown without the keyframe before them.

Fast copies the video and sound data into the new file without decoding or re-encoding anything. That is quick, even for long videos, and the picture and sound do not change, because their data is copied as it is. To make it work, the tool moves your start back to the nearest keyframe at or before it. The small marks at the bottom of the timeline show where the keyframes are, the hatched area shows the extra footage that will be included, and the line under the mode buttons tells you the real start time before you cut. The end is not tied to keyframes: the clip runs until the last frame that begins before your end time.

Precise decodes the video and encodes it again from the frame you chose. It uses the same codec as the original when your browser can encode it, and another one that fits the file type when it cannot; the result shows which one was used. Re-encoding takes longer and changes the picture slightly, as every new encoding does, and the file size can change. The sound is copied unchanged when the file type allows it, and re-encoded otherwise; the result tells you which happened.

Which mode should you use? If a second or two of extra footage at the start does not matter, or the video has frequent keyframes, choose Fast. If the clip must begin on a particular frame, for example on a word or a beat, choose Precise.

Which videos work, and what is kept

The tool reads MP4, MOV, WebM and MKV containers and writes the same type back, so an iPhone MOV stays a MOV and a WebM stays a WebM. In Fast mode the codecs inside are not touched, so H.264, HEVC, VP9, AV1 and others are all copied as they are, together with every sound track. The orientation flag of phone videos is carried over, so portrait clips stay upright. Other formats, such as AVI or MPEG transport streams, are not supported.

The preview uses your browser's own video player. If it cannot play a file, for example because of a codec it does not support, the tool still reads the length and the keyframes and can cut the file; type the times instead of watching for them. The sizes shown in the tool count 1 KB as 1,024 bytes and 1 MB as 1,024 KB.

iPhone, iPad, Android and older browsers

Fast mode only reads and writes files, so it does not need any video encoder. Precise mode needs the WebCodecs VideoDecoder and VideoEncoder of your browser. According to MDN's compatibility data these exist in Chrome and Edge 94 and later, Firefox 130 and later on the desktop, and Safari 16.4 and later, on iPhone and iPad as well. They are missing in Firefox for Android, so Precise is not available there.

When the sound has to be re-encoded in Precise mode, which happens with WebM and MKV files, the browser also needs AudioDecoder and AudioEncoder. MDN lists those for Safari only from version 26, so on an iPhone or iPad with an older system, Precise can still work for MP4 and MOV files, where the sound is copied, but not for WebM or MKV files with sound. The tool tests all of this when you open a file and when you cut it, and tells you plainly when something is not possible instead of guessing.

Phones also have less memory than computers. The new file is built in memory before you download it, so a very long, high resolution video can fail on a phone. Cutting a shorter part helps.

How to trim a video

1. 1Drop an MP4, MOV, WebM or MKV video on the box, or choose it from your device.
2. 2Drag the start and end handles on the timeline, type the times, or play the video and press Set to current time. Use the frame buttons to find the right frame.
3. 3Choose Fast or Precise. In Fast mode, check the real start time shown below the mode buttons.
4. 4Press Cut video, check the result in the player and press Download video.

Need only the sound of the clip? Use the audio extractor or the MP4 to MP3 converter, and the audio trimmer for sound files. To keep the picture and drop the sound, use Mute Video.

How it works

The tool runs on Mediabunny, an open-source media library licensed under MPL-2.0. It reads the container, finds the keyframes from the file's index and, in Fast mode, copies the encoded packets into a new container without decoding them. In Precise mode it uses your browser's WebCodecs encoders. The work runs in a background thread, so the page stays responsive, and you can cancel it at any time.

Sources

• MDN: EncodedVideoChunk.type: a key chunk does not rely on other frames for decoding
• Mediabunny: Converting media files: copying without re-encoding, trimming and why a copied region may expand to key frames
• MDN: VideoEncoder and VideoDecoder browser compatibility
• MDN: AudioEncoder and AudioDecoder browser compatibility

Built by Tobias Kurth, designer. Updated October 14, 2026.

Frequently asked questions