: Use the built-in Microsoft Photos or Video Editor app. Create a "New video project" and drag your MP4 files into the storyboard to combine them.

: A simple web-based joiner that works on any browser (Mac, Windows, iOS, or Android) for files up to 500 MB. Desktop & Mobile Apps

: A reliable free option where you can use the "Merge videos" quick action to stitch clips together.

: If you want to merge clips without losing quality or re-encoding, tools like Shutter Encoder are highly recommended by the video editing community .