All those URLs embed by default, using Iframely. Do you have "display previews of links" turned on in your settings?
oh. I must have turned it off. When I was new, I didn't know what that meant, and I remember thinking it sounded weird, like it was going to excerpt articles in a weird way. I had no idea it meant "show youtubes". Amending my request. Thanks @atomicthumbs
Oh, I can't update this.
Well, someone, feel free to close this, or edit it to:
title: Clarify what the iframely embed option does
text: People who are easily confused, like me, may not understand what the iframely preview option means, and it could be clearer.
My attempt:
old:
We use a service provider, iframely (privacy policy), to generate these. If you don't want to load content from iframely, uncheck this box. Some previews require you to load content from other sites in addition to iframely; we'll prompt you before new sites do this, and you can turn them off later through iframely's site.
new:
By "preview" we mean that we will embed linked content in posts to display them to you. For example, instead of a Youtube URL, you will see the video; instead of a soundcloud URL, you will see a player. This is the typical behaviour that you may have experienced on other social websites. Please note that we use a service provider, iframely (privacy policy), to generate these. If you don't want to load content from iframely, uncheck this box. Some previews require you to load content from other sites in addition to iframely; we'll prompt you before new sites do this, and you can turn them off later through iframely's site.
selenotrope
I'm sure there was some consideration given to this and maybe it's not desired.
But personally, I'd rather see a youtube's still image that I can play or not play rather than a text-only youtube URL that I have to click through before determining that I do or do not actually want to see it. Having to click through feels more like rolling the dice (the video will autoplay), whereas a still image isn't very disruptive and lets you move on if it's not your bag.
oEmbed is pretty easy to support in my experience and "just works".
Developer documentation: https://oembed.com/