MP4 vs WebM: Which One Should You Actually Use?

MP4 and WebM are both containers. Think of a container as the box, not what's inside it. The actual compression happens in the codec wrapped inside that box, and the codec is what really determines file size, quality, and compatibility. Here's what's actually different, and a straight answer for which one to pick.

What's inside each container

MP4 almost always contains H.264 video (sometimes called AVC) paired with AAC audio. H.264 is a 2003 standard that's been refined for over two decades. Every phone, browser, smart TV, and game console made in the last fifteen years has dedicated hardware built in specifically to decode it efficiently, which is why H.264 video plays smoothly even on modest hardware, using very little battery.

WebM was created by Google specifically to be a royalty-free alternative for web video. It wraps VP8 or VP9 video (VP9 being the modern, much more common choice) with Opus or Vorbis audio. VP9 achieves meaningfully better compression than H.264, typically 30-50% smaller files at equivalent visual quality, but VP9 encoding is significantly slower (often 5-10 times slower than H.264), and while hardware decode support for VP9 is now widespread on anything made after roughly 2016, hardware encode support is still limited, meaning VP9 relies more on software processing.

The licensing difference that started all of this

H.264 is licensed by a patent pool; the fees are typically absorbed by device manufacturers and software vendors rather than passed to end users directly, but the licensing overhead is real and it's specifically what motivated Google to build VP8/VP9 and the WebM container in the first place, a genuinely royalty-free alternative for open web video, with no patent licensing chain behind it at all.

Compatibility, as of now

For years, the standard advice was "use MP4 for compatibility, WebM if you control the whole playback environment," because Safari didn't support WebM at all. That changed with WebM support added to Safari and iOS. As of 2026, the remaining compatibility gap is limited to genuinely outdated devices (pre-2018 iPhones, pre-2017 Macs), which is a shrinking and already-small audience for most purposes.

The practical answer

If file size and bandwidth matter more than absolute universal compatibility, embedding video on your own website, for instance, WebM/VP9 is the better choice; the file-size savings are real and the compatibility gap is now genuinely small.

If you need to guarantee playback everywhere with zero exceptions, sending a file to someone else, uploading to a platform that specifies its own required format, or archiving for long-term storage where you don't control future playback software, MP4/H.264 remains the safer default specifically because of its universal hardware decode support.

If you're not sure and just need "the one that works everywhere without thinking about it": MP4.

Converting

MP4 to WebM runs entirely in your browser using the same remux-where-possible approach that makes container conversions fast rather than a full slow re-encode when the underlying codecs allow it.

Related tools

If you actually just need a smaller file rather than a specific different format, try Compress Video first. It may get you the size reduction you're after without needing to change format at all.