Content type
mastodon_post — caption optional. Up to 4 images or video. GIFs are kept as GIF. No meta keys.
Limits
JPEG / PNG / GIF / WebP. Video MP4 or MOV.
Platforms
Mastodon
Posts on any instance. Connect asks for the instance URL, then runs OAuth there.
Connect asks for the instance URL, then runs that instance’s OAuth. How the browser flow works: Connect accounts.