Introduction Some time ago, while exploring Slack’s Block Kit reference, I noticed something peculiar: the video block. When I saw that it accepted a video_url, the first thing I thought was: how does it distinguish between any content and an actual video? Would there be any particular requirement or limitation in the embed? Foreign sources? Yeah, no. There is no runtime check, other than checking the provided video_url is accessible and responds with a 2xx or 3xx code. After those checks, it’s.