Are you looking to these clips into a story with music, or do you just need to combine several long files into one big file?

If you want to merge videos without losing quality (no re-encoding):

: You can use the concat command to join clips losslessly. You create a text file listing your clips and run a command like ffmpeg -f concat -i filelist.txt -c copy output.mp4 .

To put together a "feature" (full-length video) from MP4 clips, you can use various tools ranging from simple online joiners to professional editing software.

For larger projects or more control, use these desktop applications: