How can I crop a mp4 video and cut a part of it in Windows?

There are many open-source software options available to solve this problem; you don’t necessarily need to use paid software. You can try Avidemux—it’s an open-source video editor that allows you to crop an mp4 video using lossless stream copying and perform basic format conversion tasks.

Instructions: Launch the software, click File → Open, and select the target MP4 file. Set both video and audio output to Copy. Drag the timeline slider to the beginning of the clip and click the A button; move the slider to the end of the clip and click the B button. Then, click File → Save → Save Video, and name the exported file.

Its advantages include: lossless editing, a built-in task queue for scheduling multiple editing tasks, and fast export enabled by stable stream-copying technology.

Its disadvantages include: more complex usage; lack of native one-click batch editing support; occasional compatibility issues with MP4 videos containing special codecs; and severely limited built-in tool functionality when cropping MP4 videos.

Notes

• To ensure lossless editing, be sure to set both video and audio output to Copy.
• Before exporting, confirm the positions of points A and B to avoid selecting the wrong segment.
• Do not close the software during the saving process, as this may result in a corrupted MP4 file.

This allows you to precisely crop an mp4 video clips without having to re-encode the source material. It is suitable for everyday, small-scale lossless video editing on Windows devices, as well as for quickly extracting video clips locally.