If I copy an image link from Reddit or Imgur a preview shows up in the ‘Create Post’ page. When posted, a thumbnail shows up. However when I try to do the same with art found on Twitter or Pixiv this does not work. I try to inspect the element but I can’t figure out what the difference is. Twitter’s images don’t end on a image extension (eg. ‘.png’) and has some arguments in the link (eg. ‘https://pbs.twimg.com/media/Foojf9RaEAA1GM-?format=png&name=small’, src: https://twitter.com/_denkirk/status/1624149696263651328). However Reddit’s image links are like that too and they still work. File extensions are just part of the file name and don’t actually do anything so that shouldn’t matter either. Maybe I’m just stupid.
You can always download the image and upload it to Lemmy (with link to source of course). However, I thought it would be better to use links to images hosted somewhere else in order to reduce load on the instance server. Lemmy.world hosting runs on donations so I thought it would be bad to upload lots of image data and have it serve them. Lemmy also describes itself as a ‘link aggregator’, this seems to express the preference for links over images.
Excuse my ignorance.
I got a 403 the first time I visited it, then when I went to the source, and back to the image it works. I suspect they have a cookie or something to detect that you’re a valid user.
Because this is a different domain the cookie would not come with the image request.
Just a wild guess