# Video Cutter — cut a video online

Mark the parts worth keeping as it plays. Get them back as one video.

> Mark the parts worth keeping and save them as one video in your browser. Copy mode preserves encoded frames; exact cuts and recording re-encode. No upload, works offline.

This is an interactive browser tool at https://abox.tools/trim-video/. Files are processed on the device running that browser. Any deliberate sharing or optional network feature is described on the page. What follows is its written explanation; open the address to use it.

## Your videos are **processed in your browser**. No processing upload.

Your video is read, marked, cut and written by your own browser, on your own hardware. Nothing here can fetch or send anything — there is no network feature in this tool at all — and there is no server on the other end of this page to send a video to even if there were.

- ✗ No upload
- ✗ No account
- ✗ No watermark
- ✓ As many parts as you like
- ✓ Lossless copy when compatible
- ✓ Works offline

## How to cut a video

1. **Choose a video.** Drop an MP4, MOV, M4V or WebM onto the picker. It is read straight off your disk by the browser; nothing is sent anywhere while you do it. Drop several and they are joined, in the order you put them in.
2. **Play it, and mark the parts you want.** Press `I` where a part should start and `O` where it should end. Do that as many times as you like — every pair becomes a row in the table underneath, and a band on the timeline. `U` takes the last one back, `Space` plays and pauses, and the arrow keys jump five seconds at a time. Slow the playback down if the moment is hard to catch.
3. **Fix up the marks.** Each row can be played back on its own, retimed by typing an exact time into it, moved up or down the order, or deleted. The two ends of the selected part can also be dragged along the timeline. The total at the top is what the finished video will run to.
4. **Keep them, or cut them out.** Keeping is the usual way round: the finished video is the parts you marked, joined in order. Cutting them out is the other job people want and rarely find — mark the adverts, the silences or the false starts, and what is left is joined up without them.
5. **Cut it, and download.** "Keep every byte" moves the frames across untouched. The first part can carry hidden frames from an earlier keyframe; every later part must start on a keyframe. "Cut exactly here" decodes and re-encodes every retained video frame to preserve the selected timing. The page says which method you are about to use and what it costs before you press the button.

## The longer version

[How to trim a video without re-encoding it](https://abox.tools/guides/trim-a-video/): Cutting a clip need not lose a single byte of quality. Why a cut sometimes lands earlier than you marked it, what a keyframe has to do with it, and when to accept a re-encode.

## Also in the box

- [Video Cropper](https://abox.tools/crop-video/): Cut a clip down to the part that matters.
- [Video Reverser](https://abox.tools/reverse-video/): Last frame first, sound and all.
- [Time-Lapse Maker](https://abox.tools/timelapse-video/): An hour of footage, in twenty seconds.
- [Video Frame Grabber](https://abox.tools/grab-frame/): A full-quality still from any point.

## Questions

### Is my video uploaded anywhere?

No. It is read, marked, cut and written by your own browser on your own hardware. There is no server side to this tool, and the page's `Content-Security-Policy` names every address it may contact — none of them belongs to this site. Unplug from the internet and cut a video anyway if you would rather check than be told.

### Can I keep several parts of the same video?

That is what this is for. Press `I` and `O` as many times as you like while it plays; each pair becomes a row, and the finished video is every row joined in order with everything else gone. Most online cutters give you one pair of handles and ask which single stretch to keep, which is fine for topping and tailing a clip and no use at all for watching an hour of footage once and keeping the six moments worth having.

### Does cutting lose quality?

"Keep every byte" preserves the original encoded frames and sound, so that path does not reduce quality. It is available for one section, or for several when every later section starts on a keyframe. "Cut exactly here" re-encodes every retained video frame and copies the sound when possible. "Record it as it plays" re-encodes both picture and sound. The selected method tells you which will happen before you export.

### Why does a part start earlier than I marked it?

A copied first section may carry frames from the preceding keyframe because later frames need them to decode. An edit mark asks the player to skip those initial frames; a player that ignores it can begin early. Browsers can also mishandle hidden frames at an internal join, so Copy is unavailable if any later section starts between keyframes. Choose "Cut exactly here" for those selections. It re-encodes every retained video frame; the page states the method and any initial hidden duration before export.

### Can I cut the adverts out instead?

Yes. Mark them, then choose "Cut them out": everything you did *not* mark is joined up instead, in order. The same list of marks answers both questions, so you can switch between them and see the length change without marking anything twice.

### Can I save my marks and come back to them?

Yes. "Save marks" writes a plain text file — one line a part, a start and an end separated by a comma — and "Load marks" reads one back. Two formats are offered, plain seconds and `HH:MM:SS.mmm`, and both keep to the layout other tools that work this way already use, so a file written here can be handed to one of those and a file written there can be dropped onto this page. Marking is careful work and nobody should have to do it twice.

### Which video formats can I cut?

MP4, M4V and MOV are read directly, whatever is inside them: H.264, HEVC, AV1 or VP9. Copying frames does not involve decoding them, so this path works even for a codec your browser has no decoder for at all. Anything else your browser can play — WebM most obviously — is cut by playing it and recording the result instead, which works, takes as long as the result is long, and can only keep one part. A file the browser can neither read nor play, which in practice means AVI, WMV, FLV and most MKVs, is refused with a message saying so rather than failing halfway through.

### Is there a limit on the size or length of the video?

There is no limit built into the tool, and on the copy path the file is barely read at all: the frames you keep are pointed at rather than loaded, so keeping four minutes out of a four-gigabyte recording costs about what writing those four minutes to disk costs. The exact cut walks the file a few megabytes at a time. Either way the practical ceiling is the finished file, which is assembled in memory before you download it.

### Does the sound survive?

On both MP4 paths it is copied across sample by sample without ever being decoded, so it is byte for byte what was in the file, and an edit mark keeps every part lined up with its picture to within a thousandth of a second. The one exception is joining separate videos whose sound is described differently — different sample rates, say — where there is no way to put both into one track without decoding them, and the page says so before it does. On the recording path it is captured from playback and encoded again. Either way there is a checkbox to leave it out entirely.

### Is it free, and do I need an account?

It is free, and there is no account, no sign-in, no trial and no watermark. The site carries advertising, which is what pays for it; the ads are not given anything about your video.

## How the privacy claim is verifiable

- **Processing happens in this browser.** This tool processes input and results inside your browser. Its processing code does not upload them for processing. Content-Security-Policy restricts permitted resources and connection destinations, but allowed hosts can still receive requests: the policy does not inspect payloads and alone cannot prove that nothing is sent. Compare the source with the requests for the operation you use, or complete that local operation while disconnected.
- **Nothing here fetches anything.** This tool has no network feature at all: no address to paste, nothing to download, no engine fetched on first use. Every byte that touches your video came from this origin when the page loaded.
- **On the normal path, nothing is even decoded.** On the copy path, compatible encoded frames are moved to the output unchanged. The page keeps slices pointing to the original bytes instead of decoding them. Exact cuts and recording are different: they decode and re-encode the picture locally, and the export controls identify that choice.
- **The marks file is made in the page.** Saving your marks writes a text file out of the numbers already on screen, straight to your downloads. Loading one reads it here. Neither goes near a network, and neither carries anything but times.
- **Compatible audio is copied.** On MP4 copy and exact-cut paths, compatible audio samples are copied unchanged. Joining clips with incompatible audio can decode, resample and re-encode it locally; recording also re-encodes sound. The page names these cases before export. No audio is uploaded.
- **Where frames are decoded, it happens here.** The exact cut, and the preview for a file this browser will not play, go through WebCodecs on your own machine. That is the same decoder that would show you the video anyway, running in the same place.
- **What Google loads, and what it is not given.** The ad and measurement scripts come from Google. Neither is handed anything about your video: not a file, not a frame, not a name, a size, a length, or where you cut it. Every line that reads, cuts and writes is served from this origin and listed in the repository.
- **What the donate button loads, and what it is not given.** The "Buy me a coffee" button in the header is drawn by a script from cdnjs.buymeacoffee.com and letters itself from Google Fonts. It is a link and nothing more: it reports no visit, and it is handed nothing about you or your video.
- **It works offline.** Disconnect from the network and everything on this page still works. That is the simplest proof of all.

**Check it yourself.** None of the above has to be taken on trust. This page is generated from the templates and config in the repository by a build script you can read and run yourself, and the result is committed to the `dist` branch — so you can diff what is served against what a build of the sources produces: https://github.com/A-Box-of-Tools/website

The files worth reading first are `config/site.toml` for the Content-Security-Policy, `src/segments.js` for the marks and the file they save to, `src/shared/mp4-reader.js` for the reader that finds the frames in an MP4, `src/ranges.js` for the arithmetic that turns a mark into a run of samples, and `src/copy.js` for the loop that moves those samples into the new file. None of them imports anything that can make a request.