Trim an MP4
Cut the start and end off an MP4 with no quality loss and no upload.
- Nothing is uploaded
- Works offline after first visit
- Open source
- No watermark · limit is your device’s memory; phones hold less
Trim an MP4 in your browser without re-encoding: the clip keeps its original quality and is ready in seconds. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The size limit is your device’s memory, and phones hold less; give the page a short while after one visit to save itself for offline use, and then it works offline.
Your iPhone may take a few seconds to prepare the video first, longer if it's stored in iCloud.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
Phone videos, screen recordings and downloads almost always come as MP4 with H.264 video, and they usually have a few seconds too many at each end. This page cuts them down without re-encoding: the frames between your start and end are copied into a new MP4, so the picture is identical and the file is ready as fast as it can be read.
Because an MP4 made without re-encoding has to start on a key frame, the clip may begin up to half a second before the point you set. Most phones and cameras put a key frame every second or two, so in practice the cut is where you expect it. For a frame-exact start, tick the exact option.
Your MP4 stays on your device throughout. The page runs the cut in your browser tab and saves the new file straight to your downloads.
Because the clip is copied rather than re-encoded, its file size follows the time you keep. Trim a 200 MB, four minute MP4 down to one minute and expect roughly 50 MB, give or take depending on how busy that minute is. If you need it smaller than that, the only way is to encode it again, so follow up with Compress video, which can also aim for a set size such as 25 MB for email.
The copy keeps whatever is inside the MP4: HEVC or H.264 video and AAC sound come out in the same codec at the same bitrate as before. The new MP4 is written with its index at the front, so it starts playing straight away when it is opened from a link or uploaded to a site. Ticking “Cut exactly on the frame (re-encodes, slower)” is the one case where the picture is encoded again.
How it works
- Drop the MP4, or tap to pick it.
- Set the start and end on the player, or type the times.
- Trim, and the shorter MP4 downloads.
In your browser, not on a server
Your browser plays the video from the file on your device so you can pick the start and end. Mediabunny (MPL-2.0) then reads the MP4, MOV, WebM or MKV container in your tab and copies the packets between those two points into a new file of the same type, starting from the nearest key frame within half a second. When there is none that close, or when you ask for an exact cut, the clip is decoded and re-encoded by your browser’s own video encoder (WebCodecs).
Compared with upload-based tools: Online video cutters upload the whole file just to throw most of it away, cap free videos at a few hundred megabytes and often add a watermark. Here nothing is uploaded, and a clip from a 2 GB recording is cut in seconds because the video is copied rather than re-encoded.
Verify it yourself. Give the page a short while after one visit to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Is it really lossless?
Yes, unless you tick the exact option. The encoded video and sound are copied, not decoded and encoded again, so nothing about the picture or sound changes.
Will the sound stay in sync?
Yes. Video and sound are cut from the same points and their timing is kept exactly.
How do I shorten an MP4 to fit a time limit?
Set the start where the clip should begin, then type the start plus the limit into End: for a 60 second limit starting at 12.5 seconds, type 72.5. The line under the boxes shows how long the clip will be. A fast cut can begin up to half a second early and run that much longer, so leave a second spare or tick the exact option.
Can I trim an M4V file?
Yes. M4V is the MP4 format under another name, used by iTunes and some Apple exports, and it trims the same way without re-encoding; the clip is saved with an .mp4 extension. Files protected with copy protection, such as films bought from a store, cannot be read by the page.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. Give the page a short while after one visit to save itself for offline use; then you can turn off Wi-Fi and it still works.
More video and audio tools
Trim video
Cut a clip out of a longer video without uploading it. Most cuts take seconds and keep the original quality.
Volume booster
Boost a quiet recording, turn down a loud one, or even out a batch. Done on this device, never uploaded.
Remove background noise
Keep the voice, lose the hiss, hum and fan noise. Cleaned on this device, never uploaded.
Merge audio
Combine songs, voice notes or podcast segments into one file. Done on this device, never uploaded.
Other conversions
Guides
- How to trim a video without installing an appiPhone, Android, Windows and Mac can all trim a video with what is already installed. Here is how on each.
- How to crop a videoCropping cuts away the edges of the picture, which is different from trimming the length. Here is where each device does it, and a private browser option.
- How to reverse a videoRewind effects are popular, but most phones have no reverse button. Here is where it exists, and a way to do it without installing an app.