when I use the inspect element option on the browser page and move it to the CSS of the tiktok and instagram embed, the css works, but when I put this CSS code in the discourse, it doesn’t change anything
I was removing the huge white background from the embedding of instagram posts and putting a thin border of 1px and a rounded border of 50px, the same I did for tiktok which also reduced the size of the post, as it appears cropped on mobile, but nothing is changed
You generally can’t manipulate the content of an iframe originating from a different domain due to the same origin policy — without this kind of restriction you could, for example, replace an image with CSS that makes it look like an instagram user posted something that they didn’t.
You can manipulate the iframe tag itself (add borders, round corners, etc), but generally the content within is entirely off-limits. Some services provide embed options, twitter for example has some on https://publish.twitter.com/