Is there a module or something similar I can use to replace a YouTube URL with the actual video in a node and also in comments?
I've found a few that work for the node, but what about in comments as well?
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Sign up to join this communityUse the Googtube module for this. It will provide you with an additional input format, which you can use wherever you want.
From the project page:
Googtube allows users to embed Youtube, Vimeo and Google Videos in a simple way without tags. When users post a url to videos the link is automatically converted to a video witch is actually embed code.