YouTube tags are not the same thing as hashtags typed in a description. Tags are the keyword list attached to the video. Some videos publish that list, and some do not.
Get the video link
Copy the public link for one video or Short. Playlists, channels, and clips without a video id are rejected.
Read the tags next to the description
Paste the link on YouTube title and description copy. When the video has public tags, they appear as chips under the description. Copy tags joins them with commas, which is the usual way to paste a tag list into another video's tag field.
If the list says there are no public tags, the channel did not publish any. The tool does not invent keywords.
What this page will not copy
Subtitles and transcripts are not part of the tag list, and this site does not fetch them. The title and description are available on the same result if you need the visible text as well.