Extensions, the official API and its quota, and how to pull comments for a whole channel without babysitting it.
For one video, an extension or a copy and paste will do. For a channel, or for anything you need to repeat, use something that pages through properly and writes straight to a file. The interesting part is what happens in between, because that is where most exports quietly go wrong.
Plenty of them exist and they do work on a single popular video. Their limits show up fast: many stop after the first page of comments, most skip replies, and the free ones tend to cap the number of rows exactly where your video gets interesting. If the export is a one-off and the video is small, take this route and move on.
This is the correct route in the sense that it is official, documented and permitted. It gives you comments with their replies, author, like count and timestamps, and it pages cleanly.
The catch is the quota. Every Google Cloud project gets a daily allowance, and comment requests eat into it alongside everything else that project does. Exporting a channel with a long comment history is exactly the kind of job that hits the ceiling, and when it does, everything else on that project stops too. You can request more, which is a form and a wait.
The second catch is plumbing. OAuth or an API key, paging tokens, retries, and a schema you have to flatten yourself before it becomes a CSV.
If what you want is a file with one row per comment, skip the plumbing. Our comments dataset is billed per comment listed, at $0.35 per 1,000, which puts a busy video with 20,000 comments at seven cents.
Comments live on videos, so a channel export is two steps: list the videos, then pull comments for that list. Listing videos is billed separately and cheaply, per video listed, at $0.35 per 1,000. In practice the video list is the cheap part and the comments are the volume.
Comments from YouTube videos for sentiment, FAQ mining and research: text, likes, reply count, publication time, pinned and owner flags, top or newest first, up to 200 videos per run. Deliberately without commenter names, handles or channel ids. Pay only for delivered comments.
List every video of a YouTube channel: title, video id, duration, view count, publish date and thumbnail, plus channel name, handle and subscriber count. Paste channel URLs, @handles or channel ids. Only delivered videos are charged.