A free, open-source tool for Windows and Mac, found at mp4joiner.org . It joins files without re-encoding, preserving original quality and working quickly.
Allows you to drag-and-drop videos, rearrange them, and add more clips, then export the final file.
A popular online merger that allows you to drag-and-drop clips and add crossfade transitions.
Offers a free online tool to upload, arrange, and merge videos, which you can then trim.
You can easily join MP4 files into one, either using free software or online tools. Here are the best ways to do it, based on your needs: