MP4 vs WebM — which to ship for web video

Quick verdict

• Maximum compatibility across devices → MP4.
• Saving bandwidth on modern browsers → WebM (AV1).
• HLS streaming → MP4 (fMP4) is the industry default.

Side-by-side

Aspect	MP4	WebM
Licensing	Patented codecs	Royalty-free
Codecs	H.264, HEVC, AV1	VP8, VP9, AV1
Browser support	100%	Chrome, Firefox, Safari 14.1+
File size	Baseline	20–30% smaller at the same quality

Hybrid delivery

<video controls>
  <source src="/video.webm" type="video/webm">
  <source src="/video.mp4" type="video/mp4">
</video>

• The first compatible source wins.

See also

• .mp4 reference
• .webm reference