You should only follow indexes you trust, or <x id="START_LINK" ctype="x-a" equiv-text="<a>"/>host your own<x id="CLOSE_LINK" ctype="x-a" equiv-text="</a>"/>.
If your instance is whitelisted by Twitter, a video player will be embedded in the Twitter feed on PeerTube video share.<x id="LINE_BREAK" ctype="lb" equiv-text="<br/>"/> If the instance is not whitelisted, we use an image link card that will redirect on your PeerTube instance.<x id="LINE_BREAK" ctype="lb" equiv-text="<br/>"/><x id="LINE_BREAK" ctype="lb" equiv-text="<br/>"/> Check this checkbox, save the configuration and test with a video URL of your instance (https://example.com/videos/watch/blabla) on <x id="START_LINK" ctype="x-a" equiv-text="<a>"/>https://cards-dev.twitter.com/validator<x id="CLOSE_LINK" ctype="x-a" equiv-text="</a>"/> to see if you instance is whitelisted.
Process uploaded videos so that they are in a streamable form that any device can play. Though costly in resources, this is a critical part of PeerTube, so tread carefully.