I scanned the open codec page: https://en.wikipedia.org/wiki/List_of_open-source_codecs
I'm a little confused, is H.265 not OPEN? :-(
What OP meant is that they would like an open format on the website, which, then, can be viewed in any modern browser. I think that caniuse is a good resource in this regard.
WebM with VP9 video is a good general browser target I think:
But funnily enough, even though h264 is not open, it's a widely decoded video format as well:
I hope open standards keep winning. Overall, everyone wins with the infrastructure being openly accessible, especially the common folk.