WebM (VP9)

Optional format

Off by default — enable it in Module Manager if you need it.

Open, royalty-free web format. The one format in this list with real alpha support that's also natively supported by every modern browser — useful for footage with a transparency matte destined for a web page.

Quality

High (CRF 24), Good (CRF 31) (default), Draft (CRF 40).

Include Alpha Channel

Real transparency support, browser-native.

Always straight (unassociated) alpha — no Alpha Type choice here. Browser <video>/<canvas> alpha compositing assumes straight, so that's the only convention that displays correctly. See Alpha Channels for why some other formats offer a choice and this one doesn't.