Can I crop the picture, for example to a square?

Not with this tool. It cuts the video in time. Changing the frame shape needs a video editor.

How long does it take?

Longer than a desktop app. The encoder is ffmpeg compiled to WebAssembly and runs on one CPU core inside your browser tab, so it is several times slower than HandBrake or a native ffmpeg. In our test on a fast desktop, compressing 1080p video took about four and a half times the length of the clip, so a one-minute clip takes four to five minutes; laptops and phones are slower. The first run also downloads the roughly 32 MB encoder once.

Are my MP4 files uploaded to a server?

No. Your file is read into browser memory, processed on your own device, and released when you close the tab. Nothing is transmitted, stored, or logged at any stage.

Is there a file size limit?

Nothing is capped on our side, but the whole video and the result are held in browser memory. Clips up to a few hundred megabytes work on a desktop; larger files, or phones with little memory, can run out of memory and fail.

Which formats can I use?

MP4, MOV, M4V, WebM and MKV go in. The result is always an MP4 with H.264 video, which plays on practically every phone, browser and editor.

Updated for 2026 • 100% Free Online Video Tool

Free MP4 Video Trimmer Online

This tool trims a video in time: you set a start and end in seconds and keep only that part. It does not crop the picture. By default the video is copied without re-encoding, which is fast and lossless but starts on the keyframe at or before your start time; tick "frame-accurate" to re-encode for an exact cut. Everything runs in your browser.

Your video is processed by ffmpeg running inside this tab, so nothing is uploaded. The first run downloads the ~32 MB encoder once. In-browser encoding is much slower than a desktop app such as HandBrake: expect a 1-minute 1080p clip to take several minutes to compress or resize.

Select or drop your MP4 video

MP4, MOV, WebM and MKV are accepted. The result is always an H.264 MP4.

100% Client-Side Private Processing

Your files are processed locally on your own device. Zero server uploads, zero file storage, and zero tracking.

Zero Server Logs

How MP4 Trimming Works

Fast mode copies the audio and video streams without re-encoding, so a cut takes seconds and loses no quality. The start can land up to a few seconds before the time you set, because a cut without re-encoding has to begin on a keyframe.
Frame-accurate mode re-encodes the kept section as H.264 at high quality. It is exact but takes as long as compressing that section.
WebM and MKV files are always re-encoded, since their streams cannot be copied into an MP4.
This trims in time only. It does not crop the frame to a different shape.

Step by step

How to CROP MP4 Files in 3 Steps

1
Select your video
Drop an MP4, MOV or WebM file into the trimmer.
2
Set start and end
Enter the times in seconds. Play the preview to find them.
3
Trim and save
Save the trimmed MP4.

Common Questions

Frequently Asked Questions

Everything you need to know about the free online MP4 crop tool.

Not in the default fast mode, which copies the original streams. Frame-accurate mode re-encodes at high quality, which is visually close but not bit-identical.

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