Unfurl links as videos in Slack

Question

"Slack" can unfurl links as videos, but some services can and some cannot.

Vimeo(https://vimeo.com/) can unfurl links as videos in Slack.

TED(https://www.ted.com/talks) cannot unfurl links as videos in Slack.

Their's HTML have oembed links as <link rel="alternate" type="application/json+oembed" href="https://example.com/...
And They have embed video player.

reference: https://oembed.com/

What is their's difference?

Answer 1

According to Slack support:

Unfurling of inline videos is made possible by allowlisting specific partner domains. Currently, there is only a small number of providers which unfurl this way in Slack, such as widely adopted services like YouTube, Loom and Vimeo. Each has been added on a case by case basis. We don't have any immediate plans to add further video unfurls such as this