While MP4 is the primary container, many files are encoded with the H.264 or VP9 codecs to balance file size and visual fidelity.

For general guidance on handling HD videos in MP4 format, here are some basic points:

For legally permissible downloads (e.g., your own content, Creative Commons media), use trusted tools like yt-dlp (a command-line tool, use with caution and only on permitted sites) or browser extensions from official stores with high user ratings and transparent code.